diff --git a/book/preamble.tex b/book/preamble.tex
index 64abb14..da6c30c 100644
--- a/book/preamble.tex
+++ b/book/preamble.tex
@@ -54,8 +54,9 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % for one-sided on left margin
-%\usepackage{lineno}
-%\linenumbers
+\usepackage{lineno}
+\linenumbers
+\setlength\linenumbersep{.8cm}
 
 % for two-sided on inside margin
 %\usepackage[switch*,pagewise]{lineno}