diff --git a/yatex.el b/yatex.el
index 75a1bd9..3d61322 100644
--- a/yatex.el
+++ b/yatex.el
@@ -62,7 +62,8 @@
 
 (defvar bibtex-command (if YaTeX-japan "pbibtex -kanji=%k" "bibtex")
   "*Default command of BibTeX.
-Overridden with `%#BIBTEX CommandLine...' in the buffer.")
+Overridden with `%#BIBTEX CommandLine...' in the buffer.
+Pettern `%k' in a string will be replaced with Kanji-code mnemonic of ptex.")
 
 (defvar dvi2-command		;previewer command for your site
   (cond (YaTeX-dos	"dviout -wait=0")