Figure 3.
Comparison between bookshelf labels (top, green) and subject labels (bottom, red). (a,c) Number of labels with a given number of books; (b,d) Fraction of books with a given number of labels.
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.