diff --git a/_posts/2016-04-26-javascript-validator-for-input-number.markdown b/_posts/2016-04-26-javascript-validator-for-input-number.markdown
index 291b390..80cce02 100644
--- a/_posts/2016-04-26-javascript-validator-for-input-number.markdown
+++ b/_posts/2016-04-26-javascript-validator-for-input-number.markdown
@@ -27,4 +27,6 @@ function isNumber(evt) {
 </script>
 {% endhighlight %}
 
+**Refference:** [http://stackoverflow.com/a/7295864](http://stackoverflow.com/a/7295864)
+
 hope it usefull.
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