--- a/document/isabelle.sty	Thu Jun 13 22:53:49 2013 +0800
+++ b/document/isabelle.sty	Sun Jun 16 20:42:07 2013 -0400
@@ -103,9 +103,6 @@
 \def\isacharverbatimclose{\isacharasterisk\isacharbraceright}%
 }
 
-\newcommand{\isaliteral}[2]{#2}
-\newcommand{\isanil}{}
-
 
 % keyword and section markup
 
@@ -158,9 +155,9 @@
 \isachardefaults%
 \def\isacharunderscorekeyword{\mbox{-}}%
 \def\isacharbang{\isamath{!}}%
-\def\isachardoublequote{\isanil}%
-\def\isachardoublequoteopen{\isanil}%
-\def\isachardoublequoteclose{\isanil}%
+\def\isachardoublequote{}%
+\def\isachardoublequoteopen{}%
+\def\isachardoublequoteclose{}%
 \def\isacharhash{\isamath{\#}}%
 \def\isachardollar{\isamath{\$}}%
 \def\isacharpercent{\isamath{\%}}%