diff --git a/plan.txt b/plan.txt
index 18bf783..bf3903e 100644
--- a/plan.txt
+++ b/plan.txt
@@ -217,10 +217,25 @@ Then test it out on a computer to make sure it's not buggy from syntax.
     - https://class.coursera.org/algs4partI-010/lecture/18
     - https://class.coursera.org/algs4partI-010/lecture/19
     - https://www.lynda.com/Developer-Programming-Foundations-tutorials/Using-stacks-last-first-out/149042/177120-4.html
+    - Will not implement. Implementing with array is trivial.
 Queues
-    - see: https://class.coursera.org/algs4partI-010/lecture
+    - https://class.coursera.org/algs4partI-010/lecture/20
     - https://www.coursera.org/learn/data-structures/lecture/EShpq/queue
     - Circular buffer/FIFO: https://en.wikipedia.org/wiki/Circular_buffer
+    - Implement using linked-list, with tail pointer:
+        - enqueue(value) - adds value at position at tail
+        - dequeue() - returns value and removes least recently added element (front)
+        - empty()
+    - Implement using fixed-sized array:
+        - enqueue(value) - adds item at end of available storage
+        - dequeue() - returns value and removes least recently added element
+        - empty()
+    - Cost:
+        - a bad implementation using linked list where you enqueue at head and dequeue at tail would be O(n)
+            because you'd need the next to last element, causing a full traversal each dequeue
+        enqueue: O(1) (linked list and array)
+        dequeue: O(1) (linked list and array)
+        empty: O(1) (linked list and array)
 Hash tables
     - https://www.youtube.com/watch?v=C4Kc8xzcA68
     - https://class.coursera.org/algs4partI-010/lecture/52