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) An example tree structure visualized by TreeVis; (b) TreeVis constructed the layout by sequentially appending nodes to the main chain, which is the longest path. The node ordering used when TreeVis generated the layout is shown here. Vertical lines separate main chain and side chains.
