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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/).
TreeMaps generated by the WoS. (A) TreeMap visualization of the top 25 author keywords in the PLF bibliographic collection. (B) TreeMap visualization of the top 25 Keywords Plus in the PLF bibliographic collection.