Figure 9.
A screenshot of a pdfgui model refinement session illustrating how modern software has facilitated PDF studies. Adapted from the pdfgui manual. (Online version in colour.)
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.