diff --git a/README.md b/README.md
index 1a9ba3d..e88b8ad 100644
--- a/README.md
+++ b/README.md
@@ -478,6 +478,7 @@ line. And because of `m` flag now regular expression engine matches pattern at t
 * *Lowercase letters only*: `^([a-z])*$`
 * *Uppercase letters only*: `^([A-Z])*$`
 * *URL*: `^(((http|https|ftp):\/\/)?([[a-zA-Z0-9]\-\.])+(\.)([[a-zA-Z0-9]]){2,4}([[a-zA-Z0-9]\/+=%&_\.~?\-]*))*$`
+  See more: [In search of the perfect URL validation regex](https://mathiasbynens.be/demo/url-regex)
 * *VISA credit card numbers*: `^(4[0-9]{12}(?:[0-9]{3})?)*$`
 * *Date (MM/DD/YYYY)*: `^(0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2}$`
 * *Date (YYYY/MM/DD)*: `^(19|20)?[0-9]{2}[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])$`