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.
A: undirected. B: directed. Note: colours corresponds to the weights according to the strength of the correlation, namely black for a value higher than 0.9, blue for a value between 0.75 and 0.9, green for a value between 0.6 and 0.75, red for a value between 0.45 and 0.6 and yellow for a value between 0.3 and 0.45.
