diff --git a/src/main/org/insa/algo/utils/PriorityQueue.java b/src/main/org/insa/algo/utils/PriorityQueue.java
index 1258041..4f5bd25 100644
--- a/src/main/org/insa/algo/utils/PriorityQueue.java
+++ b/src/main/org/insa/algo/utils/PriorityQueue.java
@@ -3,18 +3,29 @@ package org.insa.algo.utils;
 /**
  * Interface representing a basic priority queue.
  * 
- * @see https://en.wikipedia.org/wiki/Priority_queue
+ * Implementation should enforce the required complexity of each method.
+ * 
  */
 public interface PriorityQueue<E extends Comparable<E>> {
 
     /**
      * Check if the priority queue is empty.
      * 
+     * <p>
+     * <b>Complexity:</b> <i>O(1)</i>
+     * </p>
+     * 
      * @return true if the queue is empty, false otherwise.
      */
     public boolean isEmpty();
 
     /**
+     * Get the number of elements in this queue.
+     * 
+     * <p>
+     * <b>Complexity:</b> <i>O(1)</i>
+     * </p>
+     * 
      * @return Current size (number of elements) of this queue.
      */
     public int size();
@@ -22,6 +33,10 @@ public interface PriorityQueue<E extends Comparable<E>> {
     /**
      * Insert the given element into the queue.
      * 
+     * <p>
+     * <b>Complexity:</b> <i>O(log n)</i>
+     * </p>
+     * 
      * @param x Item to insert.
      */
     public void insert(E x);
@@ -29,6 +44,10 @@ public interface PriorityQueue<E extends Comparable<E>> {
     /**
      * Remove the given element from the priority queue.
      * 
+     * <p>
+     * <b>Complexity:</b> <i>O(log n)</i>
+     * </p>
+     * 
      * @param x Item to remove.
      */
     public void remove(E x) throws ElementNotFoundException;
@@ -36,6 +55,10 @@ public interface PriorityQueue<E extends Comparable<E>> {
     /**
      * Retrieve (but not remove) the smallest item in the queue.
      * 
+     * <p>
+     * <b>Complexity:</b> <i>O(1)</i>
+     * </p>
+     * 
      * @return The smallest item in the queue.
      * 
      * @throws EmptyPriorityQueueException if this queue is empty.
@@ -45,6 +68,10 @@ public interface PriorityQueue<E extends Comparable<E>> {
     /**
      * Remove and return the smallest item from the priority queue.
      * 
+     * <p>
+     * <b>Complexity:</b> <i>O(log n)</i>
+     * </p>
+     * 
      * @return The smallest item in the queue.
      * 
      * @throws EmptyPriorityQueueException if this queue is empty.