--- a/sandbox/jlf/samples/extension/std/doers-std.cls
+++ b/sandbox/jlf/samples/extension/std/doers-std.cls
@@ -41,7 +41,7 @@
     
 -----------------------------------------------------------------------------
 -- Mixins.
--- A Doer is an object who knows how to execute itself (understands "do")
+-- A Doer is an object which knows how to execute itself (understands "do")
 
 ::class RoutineDoer mixinclass Object public