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.
Sites are clustered along the x-axis (Factor 1) in site 5 and all other sites and along the y-axis (Factor 2) in sites 6, 7 and 1–5. See text and Table 5 for which parameters represent best each of the factors.
