diff --git a/HISTORY.md b/HISTORY.md
index a73ba45..b3aad96 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -6,6 +6,8 @@ History of SixtyPical
 
 *   Symbolic constants can be defined with the `const` keyword, and can
     be used in most places where literal values can be used.
+*   Specifying multiple SixtyPical source files will produce a single
+    compiled result from their combination.
 
 0.14
 ----
diff --git a/eg/rudiments/vector-inc.60p b/eg/rudiments/vector-inc.60p
index 6e97d74..69a69c7 100644
--- a/eg/rudiments/vector-inc.60p
+++ b/eg/rudiments/vector-inc.60p
@@ -1,3 +1,6 @@
+// This will not compile on its own, because there is no `main`.
+// But this and `vector-main.60p` together will compile.
+
 routine chrout
   inputs a
   trashes a
diff --git a/eg/rudiments/vector-main.60p b/eg/rudiments/vector-main.60p
index bffdf5e..b6e45e9 100644
--- a/eg/rudiments/vector-main.60p
+++ b/eg/rudiments/vector-main.60p
@@ -1,3 +1,6 @@
+// This will not compile on its own, because `printa` and `printb` are not defined.
+// But `vector-inc.60p` and this together will compile.
+
 vector routine
   trashes a, z, n
     print