\begin{acknowledgments}
This work was produced using the following open source software projects:
\begin{description}
\item[\href{http://www.tug.org/texlive/}{\TeX live}/%
      \href{http://www.ctan.org/}{CTAN}]
  Typesetting.
\item[\href{http://sourceforge.net/projects/pgf/}{PGF}/%
      \href{http://asymptote.sourceforge.net/}{Asymptote}]
  Graphics programming.
\item[\href{http://www.python.org/}{Python}]
  General purpose scripting.
\item[\href{http://www.scons.org/}{SCons}]
  Build manager.
\item[\href{http://www.gnu.org/software/emacs/}{GNU Emacs}]
  Text editor.
\item[\href{http://git-scm.com/}{Git}]
  Version control.
\item[\href{http://www.gnu.org/}{GNU}/%
      \href{https://www.kernel.org/}{Linux}/%
      \href{http://www.gentoo.org/}{Gentoo}]
  Operating system and distribution.
\end{description}
and many, many more.  I am deeply indebted to all of the smart,
generous people who produce such wonderful tools.

\sawsim\ work was supported by National Institutes of Health Grants
R01-GM071793.
\end{acknowledgments}
