Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Network map of the co-occurrence matrix for the 547 documents published in DSE research. VOSviewer software (version 1.6.15, Leiden University, The Netherlands) was used to map the frequency of keyword co-occurrence networks. Differences in font size imply differences in relevance. The different colours refer to the groups or clusters formed.
