An official website of the United States government
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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Network visualization map of the index keywords (keyword threshold = 2; display 174 out of 559 keywords). Each colour represents different patterns of co-occurrences based on multiple keywords retrieved from the dataset.