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.
A diagram of all fields in the database showing the relationships between them. Fields included in this dataset are shown with a coloured background. Rectangular boxes indicate content types and oval boxes are variables with a fixed vocabulary.
