diff --git a/src/Parser.php b/src/Parser.php
index a47d3cd..a2ee86e 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -5,7 +5,7 @@
 
 /**
  * JMESPath Pratt parser
- * @link http://hall.org.ua/halls/wizzard/pdf/Vaughan.Pratt.TDOP.pdf
+ * @link https://dl.acm.org/doi/10.1145/512927.512931
  */
 class Parser
 {
diff --git a/src/Utils.php b/src/Utils.php
index b4b17ca..9ed3860 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -192,7 +192,7 @@ public static function add($a, $b)
      * @param callable $sortFn Callable used to sort values
      *
      * @return array Returns the sorted array
-     * @link http://en.wikipedia.org/wiki/Schwartzian_transform
+     * @link https://en.wikipedia.org/wiki/Schwartzian_transform
      */
     public static function stableSort(array $data, callable $sortFn)
     {