fix

ps-grammar/sfb/review.jsgf

@@ -6,7 +6,7 @@ public <review> = [tobi] [please] (<follow> | <observe> | <teach> | <locate> | <
 <observe> = (start observing | observe | ([take a] look [(at this | here)] ));
 <leave> = leave;
 <continue> = continue;
-<stop> = (stop [observing | it]);
+<stop> = (stop [it]);
 <teach> = ( (this is [a | an | the] ) | ( these are [the] ) ) <object>;
 <locate> = ( ( where is [a | an | the] ) | ( where are [the] ) ) ( <object> | <furniture> );
 <list> = ( which objects do you know ) | ( list [the] objects );