Figure 6.
Author’s keyword co-occurrence network. Nodes represent keywords, and the connection between nodes indicates the coexistence of terms in the same document. The size of the circle indicates the degree of the node.
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.