\def\ChezScheme{\textsl{Chez Scheme}}
\def\PetiteChezScheme{\textsl{Petite Chez Scheme}}
\def\CSUG#1{\hyperlink{http://www.scheme.com/csug#1/}{\emph{Chez Scheme Version #1 User's Guide}}}
\def\TSPL#1#2{\hyperlink{http://www.scheme.com/tspl#1/}{\emph{The Scheme Programming Language, #1#2 edition}}}