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.
Flow diagram showing study selection process. CENTRAL, the Cochrane Central Register of Controlled Trials in The Cochrane Library; CNKI, Chinese National Knowledge Infrastructure; CBM, Chinese Biomedical Literature Database; CHM, Chinese herbal medicine.
