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.
Bubbles. This figure illustrates three simple bubbles and two complex bubbles. Simple bubbles are A-C, B-D and E-F. The first complex bubble starts at A and ends at D while the second one starts at D and ends at F. (X-Y is the subgraph that starts at X and ends at Y). Complex bubbles are solved by executing the simple bubble-solving algorithm and path-collapsing algorithm.
