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.
The content is available as a PDF (67.3 KB).
The online version of the original article can be found at 10.1007/BF03405152
