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 A-domain is decomposed into three parts because of the two insertion domains, i.e. B and B′. A1 part is composed of α1–α2 and β1–β3. A2 part is composed of α3–α6 and β4–β7. A3 part is composed of α7–α8 and β8.
