diff --git a/snippets/ENSURE/Unidirectional_Dependency.mp b/snippets/ENSURE/Unidirectional_Dependency.mp
new file mode 100644
index 0000000000000000000000000000000000000000..299d0feb7870bce3c13b944d4ef3e18cc43b14ab
--- /dev/null
+++ b/snippets/ENSURE/Unidirectional_Dependency.mp
@@ -0,0 +1,4 @@
+/* Ensure that if event A appears exactly once, then event B 
+appears exactly once.  Change the numbers as needed. */
+
+ENSURE #A == 1 -> #B == 1;