diff --git a/graph.rkt b/graph.rkt
index a79f8b9..da1d357 100644
--- a/graph.rkt
+++ b/graph.rkt
@@ -110,6 +110,8 @@
   (define (matrix-graph? g)
     (g:matrix-graph? (gg g)))
 
+  ;; 3 Graph properties are not supported.
+
   ;; 4 Basic Graph Functions
   ;; 4.1 Breadth-first Search
   (define (bfs g source)
@@ -162,6 +164,8 @@
   ;; 2.3 Matrix Graphs
   [matrix-graph? (-> Graph Boolean)]
 
+  ;; 3 Graph properties are not supported.
+
   ;; 4 Basic Graph Functions
   ;; 4.1 Breadth-first Search
   [bfs (-> Graph Any (Values (Mutable-HashTable Any Number)