diff --git a/src/I18n/PluralRules.php b/src/I18n/PluralRules.php
index <HASH>..<HASH> 100644
--- a/src/I18n/PluralRules.php
+++ b/src/I18n/PluralRules.php
@@ -132,6 +132,7 @@ class PluralRules {
  * @param int|float $n The number to apply the rules to.
  * @return int The plural rule number that should be used.
  * @link http://localization-guide.readthedocs.org/en/latest/l10n/pluralforms.html
+ * @link https://developer.mozilla.org/en-US/docs/Mozilla/Localization/Localization_and_Plurals#List_of_Plural_Rules
  */
 	public static function calculate($locale, $n) {
 		$locale = strtolower($locale);
Add another reference link for the plural rules.