--- a/ChengsongTanPhdThesis/Chapters/Introduction.tex	Sun Jun 12 17:03:09 2022 +0100
+++ b/ChengsongTanPhdThesis/Chapters/Introduction.tex	Tue Jun 14 18:06:33 2022 +0100
@@ -37,6 +37,7 @@
 
 \newcommand\myequiv{\mathrel{\stackrel{\makebox[0pt]{\mbox{\normalfont\tiny equiv}}}{=}}}
 
+\def\bnullable{\textit{bnullable}}
 \def\Some{\textit{Some}}
 \def\None{\textit{None}}
 \def\code{\textit{code}}
@@ -52,6 +53,7 @@
 
 \def\fuse{\textit{fuse}}
 \def\bder{\textit{bder}}
+\def\der{\textit{der}}
 \def\POSIX{\textit{POSIX}}
 \def\ALTS{\textit{ALTS}}
 \def\ASTAR{\textit{ASTAR}}