|Year : 2023 | Volume
| Issue : 6 | Page : 497-507
Bibliometric analysis and visualization of the extrahepatic portal venous obstruction publication landscape
Anjan Kumar Dhua1, Mohit Garg2, Devendra Kumar Yadav1, Prabudh Goel1, Vishesh Jain1, Sachit Anand1, Ajay Verma1
1 Department of Pediatric Surgery, AIIMS, New Delhi, India
2 Central Library, Indian Institute of Technology, New Delhi, India
|Date of Submission||23-Mar-2023|
|Date of Acceptance||29-Jul-2023|
|Date of Web Publication||02-Nov-2023|
Anjan Kumar Dhua
Department of Pediatric Surgery, Room No. 4002, Teaching Block, AIIMS, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: A scientometric analysis was conducted to characterize the global research publications in extrahepatic portal venous obstruction (EHPVO), and state-of-the-art visualization graphics were generated to provide insight into specific bibliometric variables.
Materials and Methods: The Web of Science database was accessed for research productivity and bibliometric variables of countries, institutions, authors, journals, and content analysis of top-20 cited documents were performed. Collaborative networks and co-occurrence of keywords map were generated using VOSviewer software.
Results: Two hundred and sixteen records were retrieved with an annual growth rate of 2.53%. India is the leading country in productivity (n = 4339), followed by the USA and China. Post Graduate Institute of Medical Education and Research, Chandigarh, was the top productive institute. Sarin SK was the most prolific author, having the highest citations received and h-index. The hotspot topics were “portal hypertension,” “cirrhosis,” “children,” “biliopathy/cholangiopathy,” “liver fibrosis,” and “liver transplantation” as per keyword co-occurrence networking. J Gastroenterol Hepatol had the most publications of EHPVO research as well the h-index. Regarding collaborative network mapping, the USA and Primignani M were the significant nodes among country and author, respectively.
Conclusion: EHPVO research publication volume is low but is gradually progressing with dominant contributions from Indian institutes and authors. Most highly cited articles are of low level of evidence, and multi-institutional collaborative research can be the way forward.
Keywords: Bibliometric study, citation analysis, extra-hepatic portal venous obstruction, keyword co-occurrence mapping, scientometrics, VOSviewer
|How to cite this article:|
Dhua AK, Garg M, Yadav DK, Goel P, Jain V, Anand S, Verma A. Bibliometric analysis and visualization of the extrahepatic portal venous obstruction publication landscape. J Indian Assoc Pediatr Surg 2023;28:497-507
|How to cite this URL:|
Dhua AK, Garg M, Yadav DK, Goel P, Jain V, Anand S, Verma A. Bibliometric analysis and visualization of the extrahepatic portal venous obstruction publication landscape. J Indian Assoc Pediatr Surg [serial online] 2023 [cited 2023 Nov 28];28:497-507. Available from: https://www.jiaps.com/text.asp?2023/28/6/497/389329
| Introduction|| |
Extrahepatic portal venous obstruction (EHPVO) is one of childhood's most common causes of upper gastrointestinal (UGI) bleeding. EHPVO is characterized by a chronic blockage of the portal venous blood supply leading to portal hypertension and its downstream effects in the setting of a well-preserved liver function. EHPVO is a major cause of portal hypertension (54%) and UGI bleeding in children (68%–84%) from the developing world. In contrast in the West, noncirrhotic nontumoral portal venous thrombosis is the second most frequent cause of portal hypertension in adults, whereas in children, it constitutes a small proportion (11%).
In EHPVO, the natural history is complex because of early insult. It is compounded by growth failure, slow but progressive parenchymal extinction, impaired quality of life, minimal hepatic encephalopathy, and portal biliopathy. Tremendous efforts by authors in the past and ongoing advanced basic and clinical research have been enlightening gastroenterologists, surgeons, pediatricians, and researchers focused on EHPVO, covering several aspects of EHPVO such as its etiology, genetics, role of liver biopsy, radiological aspects, endoscopic eradication of varices, and shunt surgery. We envisaged assessing the publication landscape of EHPVO and summating it in a scientometric approach by conducting a bibliometric study.
In this respect, scientometrics (Literally: Measurement of science) is an information science-related scientific field that evaluates the progress, structure, productivity trends, quality, and collaboration of scientific work generated over the years. The availability of scientometric (e.g., citation rate and H-index) and state-of-the-art visualization techniques (e.g., three-point chart, collaboration maps, etc.) can be used to assess the publication landscape both qualitatively and quantitatively in a scientific way. Specifically, the tools can be used to assess the quality and quantity of research activity for the distinct areas of science generated in terms of countries, single institutions, single periods, or single authors. This kind of bibliometric analysis is expected to showcase the key scientists/authors, research trends, journals, institutes, and high-yield areas already trodden. Therefore, our results can direct young and future scientists to plan their research avenues in a more informed and efficient way. Recent studies similar to our endeavor have applied bibliometric analysis to present the overview of a specific research area. Among these studies, it is worth mentioning that some pediatric surgery conditions, namely posterior urethral valve, anorectal malformation, esophageal atresia, choledochal cyst, Hirschsprung's disease, etc., have been dealt with similarly comprehensively.,,,, To the best of our knowledge, no bibliometric study of literature on EHPVO has been conducted.
Thus, this study used a scientometric approach to comprehensively review, evaluate, measure, and visualize the publication landscape on EHPVO. The specific objectives were to examine the trend of EHPVO research output over time and recognize prolific scholars and their contributions to the field of EHPVO. A content analysis of the top 20 articles (10th percentile) was performed to get an insight into the high-yield topics in terms of citations accrued over time. To generate collaboration network maps across countries, institutions, and authors using text-mining software. Furthermore, keyword co-occurrence maps were developed to understand the hotspot areas of EHPVO publication.
| Materials and Methods|| |
The entire procedure for conducting bibliometric analysis in this study, including data collection, screening, extraction, and synthesis is presented in this section.
The Web of Science™ (WoS)(https://www.webofscience.com/wos/woscc/advanced-search) was queried on February 28, 2023 with a search string ([TS=(EHPVO)] OR TS=[”Extrahepatic portal venous obstruction”]). The search field was set to “Topic Search-TS” to select all manuscripts that contain the search terms in the search logic mentioned above in their title, abstract, list of author keywords, or list of keyword plus.
The records were collected by exporting them to.text files for further analysis.
Bibliometric analysis and software package
This study employed Bibliometrix R-package software, an open-source software that provides tools for conducting quantitative research in bibliometrics. R-package was developed by Aria and Cuccurullo and written in the R language. R is a programming language for statistical computing and graphics supported by the R Core Team and the R Foundation for Statistical Computing. It has the main algorithms for conducting statistical and science mapping analysis. The recent versions of the Bibliometrix R-package (i.e., 2.0 upwards) contain a web interface app (Biblioshiny) introduced to aid users without coding skills in conducting bibliometric analysis. The Biblioshiny interface allows for data importing from the files downloaded from the databases and their analysis.
Co-occurrence analysis helps researchers identify the hot topics and research trends in a scientific discipline. The strength of this relationship between articles can help researchers identify the intellectual base of the discipline, research frontiers, influential authors, and other relevant bibliometric information. VOSviewer software (version 1.6.19(0) from http://www.VOSviewer.com/; Leiden University, Netherlands) is a software tool for building and depicting networks based on bibliometric data. It features a text mining instrument that can depict co-occurrence networks of authors and terms extracted from any part of scientific literature. The co-authorship link generation function was utilized in the current study with parameters set to “country” co-authorship and “author” co-authorship links. The output is presented as network visualization maps. For clarity, the terminology used to describe VOSviewer maps is being presented. Maps created, visualized, and explored using VOSviewer include items. Items are the objects of interest. Items may, for example, by researchers, countries, or keywords. Between any pair of items, there can be a link. A link is a connection or a relation between two items. Examples of links are co-authorship links between researchers and co-occurrence links between keywords. A map normally includes only one type of link. Furthermore, between any pair of items, there can be no more than one link. Each link has a strength, represented by a positive numerical value. The higher this value, the stronger the link. The strength of a link may, for example, indicates the number of publications two researchers have co-authored (in the case of co-authorship links). Sometimes, the links between all items have a strength of one. VOSviewer then does not show the strength of a link. Items and links together constitute a network. Hence, a network is a set of items with links between the items. In VOSviewer maps, the size of the label and the circle of an item are determined by the item's weight. The higher its weight, the larger its label and circle. The color of an object is determined by the cluster to which the article belongs. Lines between items represent links. The distance between two items in the visualization approximately indicates the relatedness of the items in terms of co-authorship or co-occurrence link.
Keyword co-occurrence network
In keyword co-occurrence network (KCN), each keyword is represented as a node, and each co-occurrence of a pair of words is represented as a link. The number of times a pair of words co-occur in multiple articles under review generates the weight of the link connecting the pair. The network map constructed in this manner represents cumulative knowledge of a scientific theme and helps to uncover meaningful insights based on the patterns and strength of links between keywords that appear in the literature. VOSviewer was used to generate KCN graphics based on text mining property inherent to the software.
The primary data were downloaded from WoS; the current analysis was meant to generate secondary data from the existing data, and no interaction with animal or human subjects was involved. Since this approach had no ethical issues, ethics committee clearance was not sought.
| Results|| |
A total of 216 records were obtained from the WoS database. An overview of the data is presented in [Table 1].
|Table 1: Overview of the main information, document contents, author's collaboration and document types|
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The annual growth rate was found to be 2.53%. The productivity is superimposed with the mean total citation per article per year and shown in [Figure 1].
|Figure 1: Graph depicting the year-wise production and mean citations per article per year and the arrows showing the visual trend of annual production over the years|
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The top country in terms of research article productivity was India (n = 227), followed by Italy (n = 52) and France (n = 34). A choropleth map depicting the productivity of various countries is shown in [Figure 2].
|Figure 2: Choropleth map of the world showing the country-specific productivity and distribution|
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When only the corresponding author's county is considered, the top 10 countries are shown and further characterized as single country publication and multiple country publication in [Figure 3].
|Figure 3: A bar graph showing the top ten productive countries in terms of the corresponding authors of the publications. They are the relative distribution of single-country publications and multiple-country publications. SCP: Single-country publications, MCP: Multiple-country publications|
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The top 10 most cited countries are shown in [Table 2]. India is at the top, followed by Italy and the United Kingdom.
|Table 2: Demonstrating the top cited countries along with their average article citations|
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The top 10 institutes involved in EHPVO publications are shown in [Figure 4]. Postgraduate Institute of Medical Education and Research, Chandigarh, India, leads the rankings, followed by Sanjay Gandhi Institute of Postgraduate Institute, Lucknow, India, and Govind Ballabh Pant, Hospital, Delhi, India.
|Figure 4: The production of the most relevant affiliations related to extra-hepatic portal venous obstruction research|
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The top 10 prolific authors in EHPVO publications are tabulated in [Table 3]. However, when citations received by the authors are considered the top 10 authors are as per depicted in [Table 3] (under the citations column). When arranged as per the impact of authors using h-index as the metric, the list of authors is provided in the columns with the heading H-index.
|Table 3: Top ten rankings in terms of author's production, citations received, and H-index|
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The 20 top-cited articles with content analysis variables are tabulated in [Table 4].
|Table 4: Top-cited 20 articles and their bibliometric metrics (TC and TC per year), along with the article type, type of research, topic dwelled, and level of evidence|
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Content analysis of the top twenty articles was done by categorizing them into the type of article-original paper, narrative review article, editorial, or any other; and type of research in terms of basic science research, clinical research, literature review, expert panel opinion; and the topic covered. These articles were published between 1965 and 2014. The total citations of these articles ranged from 259 to 63 (median – 108.5). Considering the year of the publication, the total citation per year was calculated, ([Citations received/2023-year of Publication]), which ranged from 19.1 to 1.2. The article by Webb LJ, et al. published in the QJM: An International Journal of Medicine journal had the highest total citation count (259) and received 5.9 total citations annually. This original article is based on clinical research on the clinical profile, management, and outcome of 97 EHPVO patients presenting to the Royal Free Hospital, London, between 1960 and 1976. Regarding the highest total citations received per year, the narrative review article by Khanna R et al. was published in the Journal of Hepatology in 2014 and deals with comprehensive coverage of EHPVO subtopics. [Table 5] summarises the overall findings of the content analysis.
The top 10 journals involved in the publication of extra hepatic biliary atresia research are depicted in [Table 6]. The various bibliometric variables considered are productivity, citations received, and their impact (H-index).
|Table 6: The top journals in terms of productivity, citations received, and H-index|
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The international collaboration between countries and authors was mapped by collecting the co-authorship links. The threshold for assessing the collaboration links between countries was a minimum of three documents. Fifteen countries met the threshold, but one was excluded because the link strength was zero. Using these criteria, 14 items in 5 clusters with 20 links and a total link strength of 29 were identified [Figure 5]. The USA stands out on the map with the most significant node among the collaborative countries (documents – 19 and link strength – 9), followed by Belgium (documents – 5 and link strength – 7) and India (documents – 118 and link strength – 7).
|Figure 5: The co-authorship map of countries. The number of collaborating countries was 14 in 5 clusters, with a total link strength of 29. Different colors indicate different clusters, and the size of the circles is proportionate to the country's output. The thickness of the lines represents the link strength of the countries. It also shows that the closer the two countries are, the stronger and broader the connections between them|
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The threshold for eligibility for collaboration links between authors was a minimum of three publications. Out of 984 authors, 48 met the criteria (having at least three publications), out of which 23 authors were found to be connected, and the rest were not. These 23 authors, when mapped, were arranged in 5 clusters with 55 links and a total link strength of 136 [Figure 6]. Primignani, M (documents – 7 and link strength – 29), de Franchis, R (documents – 6, and link strength – 26), and Buciarelli, P (documents – 5 and link strength – 24) were the top three authors in terms of collaborative links strength.
|Figure 6: The co-authorship map of authors showing the authors who have demonstrated collaboration in extra-hepatic portal venous obstruction publications. Different colors indicate different clusters, and the size of the circles indicates the number of publications. The thickness of the lines represents the link strength of the authors|
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Keyword co-occurrence network
The threshold for eligibility for generating co-occurrence links between keywords was a minimum of five publications. Out of 658 keywords, 71 met the criteria (i.e. present in at least five publications). These 71 keywords were arranged in 6 clusters with 1094 links and a total link strength of 2398 [Figure 7]. Portal hypertension (occurrence – 44 and link strength – 294), thrombosis (occurrence – 42, and link strength – 264), and children (occurrence – 43 and link strength – 253) were the top three keywords in terms of co-occurrence link strength.
|Figure 7: The keyword co-occurrence network of keywords that co-occur in extra-hepatic portal venous obstruction publications. Different colors indicate different clusters, and the size of the circles indicates the magnitude of their occurrences. The thickness of the lines represents the link strength of the keywords|
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| Discussion|| |
Research and related publications in EHPVO have gradually shown an increasing trend, which has happened in parallel with almost all scientific fields. However, the volume of publications on EHPVO is comparably less than many other pediatric surgical conditions. To put this into perspective, a bibliometric study on anorectal malformation from the WoS database published in 2022 retrieved 1510 articles. A scientometric analysis of global publications on biliary atresia from the WoS database revealed 4459 publications till 2018, while another study on esophageal atresia based on the WoS database had 2170 publications., Most pediatric surgical conditions are congenital and uncommon. Their geographical distribution is more or less equal worldwide, with some exceptions and variations. Despite their rarity, they have attracted attention from researchers from various fields, including scientists and clinicians from pediatrics, obstetrics, pediatric surgery, geneticists, anatomists, radiologists, anesthesiologists, and allied specialties. EHPVO, on the other hand, is a disease that presents in childhood beyond infancy and is managed primarily by a pediatric gastroenterologist, radiologist, and pediatric surgeons and their allied specialties. Most importantly, EHPVO has a skewed distribution geographically with a relatively high incidence in the Indian subcontinent, and its representation in the rest of the world is sparse. Excluding cirrhosis, EHPVO is the most common cause of portal hypertension globally. In the Indian subcontinent, 20%–30% of all variceal bleeds are due to EHPVO. In Japan, 10%–20% of variceal bleeds and 2%–5% of variceal bleeds in the west are due to EHPVO. Because of the atypical geographical distribution of the EHPVO cases and fewer specialties involved in their management, care, and possibly research, the production of EHPVO publications is far less than the other pediatric surgical conditions. The low annual growth rate of publication productivity of 2.53% for EHPVO also has the same basis as discussed above.
The USA has always stood out and dominated the research productivity in almost all bibliometric studies.,, It is an established worldwide trend for a large volume of scientific papers to originate from high-income countries and for authors from these countries to dominate key roles in authorship. High-end research with large funding could possibly explain this pattern. In contrast, the results for EHPVO are different. It is important to understand that the geographical distribution of EHPVO shows a higher incidence in the Indian subcontinent, as described previously, explaining the phenomena of high research output (as well as citations received) from India followed by the USA and China in terms of productivity and Italy and the United Kingdom in terms of citations received.
Several institutes from India have done seminal work in EHPVO, as evidenced by 5 out of 8 top productive institutions being from this part of the world. A spin-off observation was that all these institutes were from North India. This points toward an unexplained predilection of the north Indian population to develop EHPVO compared to the southern states of India. Simon et al., in a hospital-based retrospective study from a tertiary care hospital in South India, found that only 42% of their pediatric portal hypertension cases were from South India. They proposed that regional and ethnic differences may affect the etiology of pediatric portal hypertension cases in India.
All the top authors in terms of productivity, citations received, and h-index were from India. Sarin SK was the most prolific author, received the most citations, and was the most influential author, as evidenced by having the highest H-index.
Analyzing the contents of the top-cited articles gives us an opportunity to understand the high-yield research zones in a certain scientific field. When applied to the 20 top-cited articles, it was noted that the oldest article was published in 1965. It can be argued that old articles get more exposure to the scientific community, and hence the chances of accruing citations are also more. However, this is not always the case, as redundant articles that do not catch the attention of the researchers seldom receive high citations, indirectly indicating that the number of citations received by the article indicates the quality and relevance of a particular article in the research ecosystem. The article by Khanna and Sarin published in 2014 based on a narrative review of the medical literature on diagnosing and managing noncirrhotic portal hypertension. This paper was published 9 years ago and accrued many citations to find a place among the top 20 articles. The reason is already outlined before; additionally, it must be understood that review articles and papers that occupy the top zones of the pyramid of levels of medical evidence (systematic reviews, metanalysis, and randomized control trials) attract more attention from the readers and are bound to be cited in subsequent publications in the field. Still, the effect of duration since publication cannot be ruled out altogether; hence, we have used another metric, the “citation received per year,” to nullify the effect of duration since publication to a certain extent.
The article by Webb LJ et al., published in the QJM: An International Journal of Medicine journal in 1979, has the highest total citation count This article is an original clinical research work dealing with the presentation, management, and outcome of EHPVO. When the total citation per year was taken into consideration, the article “Noncirrhotic portal hypertension-Diagnosis and management” was authored by Khanna and Sarin and published in 2014 in the Journal of Hepatology was the highest (19.1). This article was a narrative review and covered various aspects of EHPVO in great detail.
When an attempt was made to understand the hot-spot research areas based on these twenty articles, it was noted that original clinical research work, notably on topics such as “comprehensive coverage of EHPVO subtopics,” “biliary abnormalities associated with EHPVO” and “presentation, management and outcome” in EHPVO were the high-yield topics. This points toward the fact that EHPVO is a rare childhood disease, and the clinical course, the outcome of the disease, and associated biliary abnormalities have attracted the attention of researchers in this field. Still, attempts are being made to pinpoint the exact etiology of EHPVO, as evidenced by two articles (one on JAK2 V617F mutation as an underlying etiology in EHPVO patients and the other on screening for thrombophilia). Off late, the role of restorative meso-Rex jump graft in surgical management has also attracted attention, as we can note two articles on this subject are in the top cited articles. The endoscopic approach for the control of variceal bleeds is very important in the management of EHPVO as we can see that there are two articles (one on “endoscopic sclerotherapy for bleeding esophageal varices” and the other on “n-Butyl-2-cyanoacrylate glue for endoscopic sclerotherapy”) have accrued more citations than several other topics. The majority of the highly cited articles were of low level of evidence. However, this is understandable, considering the condition's rarity and geographical heterogeneity. Designing and conducting randomized control trials is practically difficult in this scenario. Collaborative multi-institutional research could help generate a high level of evidence currently lacking.
The top-3 journals which disseminated EHPVO research were the Journal of Gastroenterology and Hepatology, the Journal of Pediatric Gastroenterology and Nutrition, and the Journal of Pediatric Surgery. This suggests that research publications on EHPVO have been of equal interest to the pediatric gastroenterology, hepatology, and pediatric surgery research community. These rankings reflect how the top journals in their respective fields have remained at the center stage to propagate the EHPVO research findings amongst the research community as the understanding and management of EHPVO have evolved over the years.
Collaboration-wise, the USA occupies a central position (with the highest link strength of 9), despite having a smaller node (lesser productivity) than India. The most collaborative authors were Primignani M (Italy), de Franchis R (Italy), and Buciarelli P (Italy), occupying a central position compared to Indian authors in the collaborative map. These findings reemphasize the importance of collaboration with national or international colleagues to stand out despite having fewer cases of a particular disease for research and publications. The thought that comes to mind when one studies the top-three keywords/terms – “Portal hypertension (occurrence – 44 and link strength – 294), thrombosis (occurrence – 42, and link strength – 264), and children, indicating the importance of portal thrombosis as a cause of portal hypertension in children. A glance at the KCN also shows that other important keywords are shunts, shunt surgery, portosystemic shunts, cirrhosis, endoscopic sclerotherapy, portal biliopathy, etc. One can also notice that some other words/terms like liver transplantation, hypersplenism, splenomegaly, hypertensive gastropathy, portal biliopathy, and cholangiopathy have also been the focus of research but lesser in comparison to others which are more centrally placed in the KCN. Off late, it has been realized that even in EHPVO, parenchymal hepatic abnormalities and biliopathy can ensue, leading to the requirement of liver transplantation later in the course of the disease.
The citation count is a dynamic value; hence, our study is akin to taking a screenshot of the publication landscape. One may also note that a citation count does not consider whether a particular citation was made with positive or negative intent in a specific manuscript. It must also be appreciated that the chances of a particular article getting cited depend on the type of article it is; for example, meta-analyses or systematic reviews tend to accrue more citations than “case reports” or “letter-to-editors.” Also, older articles get more exposure and window period to the scientific community and accumulate more citations than recently published ones.
Spelling authors' names are critical for accurate text mining and generating reliable, replicable, and error-free network maps. The same author can have different names on records, while others have the same name (homonyms). These factors can lead to inadvertent errors in generating final network maps. In VOSviewer, this has been surmounted by utilizing the “thesaurus” function. The authors had to screen for the same authors manually but with different spellings and “instruct” VOSviewer (by uploading a separate file containing these commands) to consider them like other forms of one particular spelling. However, errors related to homonyms could not have been completely eradicated. Also, the raw data from only one database has been utilized, which may be a drawback of the current study. Also, those journals not in the WoS database may have been omitted. The results of analyzing multiple databases would have been more accurate but are beyond the technical capability of the currently available bibliometric software.
| Conclusion|| |
The publications in EHPVO have been low but progressing steadily, contributed strongly by Indian institutes and authors. Despite several authors from India contributing and collaborating towards EHPVO, there is still scope for improvement compared to the high level of collaboration among non-Indian authors. Key hot-spot research areas include biliopathy/cholangiopathy, liver fibrosis/cirrhosis, and liver transplantation in EHPVO. Most highly cited articles are of low level of evidence, and multi-institutional collaborative research can be the way forward to improve this aspect in EHPVO publications.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]