diff --git a/main/math.tex b/main/math.tex
index a7af3a2..d0bf5f8 100644
--- a/main/math.tex
+++ b/main/math.tex
@@ -15,6 +15,7 @@
 \newcommand{\Z}{\mathbb{Z}}
 \newcommand{\I}{\mathbb{I}}
 \newcommand{\E}{\mathbb{E}}
+\newcommand{\D}{\mathbb{D}}
 \newcommand{\8}{\infty}
 \newcommand{\dx}{\mbox{d}}
 \newcommand{\floor}[1]{\left\lfloor #1 \right\rfloor}