diff --git a/graph.rkt b/graph.rkt
index a24beae..348ad9e 100644
--- a/graph.rkt
+++ b/graph.rkt
@@ -35,7 +35,7 @@
 
            bfs bfs/generalized fewest-vertices-path
            dfs dfs/generalized
-           dag?
+           dag? tsort
 
            graphviz)
 
@@ -173,6 +173,8 @@
      #:return finish))
   (define (dag? g)
     (g:dag? (gg g)))
+  (define (tsort g)
+    (g:tsort (gg g)))
 
   ;; 10 Graphviz
   (define (graphviz g #:output [output #f] #:colors [colors #f])
@@ -254,6 +256,7 @@
                          #:return (-> Graph Any Any))
                         Any)]
   [dag? (-> Graph Boolean)]
+  [tsort (-> Graph (Listof Any))]
 
   ;; 10 Graphviz
   [graphviz (->* (Graph)
@@ -355,7 +358,9 @@
     (check-equal? (dfs/generalized (directed-graph '((a b) (a c) (b d) (c d))))
                   (void))
     (check-true (dag? (directed-graph '((a b) (b c)))))
-    (check-false (dag? (directed-graph '((a b) (b a))))))
+    (check-false (dag? (directed-graph '((a b) (b a)))))
+    (check-equal? (tsort (directed-graph '((a b) (b c) (a d) (d b))))
+                  '(a d b c)))
 
   (test-case "10 Graphviz"
     (define g (directed-graph '((a b) (b c))))