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.
The most common author keywords. Note: the principal components of the data structure were visualized regarding the colors of the nodes; the node size was identified by the keywords’ occurrences; the closer the nodes are, the stronger the association between two keywords are.
