Figure 4.
Most common definitions ranked by the average number of citations per year since publication. Definitions with at least five citations were ranked by considering the average number of citations per year since the date of publication
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.