diff --git a/inputs/lecture_02.tex b/inputs/lecture_02.tex
index 331efb9..7c76520 100644
--- a/inputs/lecture_02.tex
+++ b/inputs/lecture_02.tex
@@ -9,7 +9,7 @@
 
 \begin{remark}
     \begin{itemize}
-        \item If $\emptyset \neq  O   \R$
+        \item If $\emptyset \neq  O \overset{\text{open}}{\subseteq} \R$
             then $O \sim \R$.
         \item If $O \subseteq \R$
             is open, then $O$ is the union of open intervals