Fig 1. Flow diagram of the study.
aDetailed description in Zock et al. 2007. bDetailed description in Rodriguez-Trigo et al. 2010.
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.