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 chart study selection. * Neither participants, concept nor context stated in title or abstract. ** Wrong participants, concept or participants stated in title or abstract. *** Reasons for exclusion (wrong participants, wrong concept, wrong context) can be found in Appendix C.
