diff --git a/doc/gmnisrvini.scd b/doc/gmnisrvini.scd
index 3fbfba1..2baa2f0 100644
--- a/doc/gmnisrvini.scd
+++ b/doc/gmnisrvini.scd
@@ -61,6 +61,11 @@ to each routing strategy. The token and match string may be omitted
 :  Regular expression routing. The string is a JavaScript-compatible regular
    expression which is tested against the URL path.
 
+See ECMAScript 2016, section 21.2 for a definition of the regular expression
+syntax and features, or an informative reference on MDN:
+
+https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
+
 Some example section names and examples of matching paths:
 
 |[ *[example.org:/foo]*