diff --git a/book/book.tex b/book/book.tex
index 1efa72e..2a894e4 100644
--- a/book/book.tex
+++ b/book/book.tex
@@ -9,6 +9,7 @@
 \usepackage{float}
 \usepackage[T1]{fontenc}
 \usepackage{tocloft}
+% \usepackage{tex4ebook}
 \usepackage{chemformula}
 \usepackage{booktabs}
 \usepackage{makecell}