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.
Grade of recommendation according to the Oxford Center for Evidence-based Medicine Levels of Evidence (May 2001).
| Color According to Recommendation | Meaning |
|---|---|
| * | Very recommendable |
| ** | Moderately recommendable |
| † | Not recommended |
| ‡ | Controversy (Neither recommended nor Disapproved) |
