The Problem of Serial Order in Behavior Lashley 1951
From enfascination
If I have my history right, this an Chomsky's book were the two works that were the beginning of the end for Behaviorism, creating a space outside of that field to ask legitimate questions that it presumably questioned the legitimacy of.
I thought of it as more of a historical paper. He provides lots of examples in language, behavior and neurology that confound the no-mental-states thing and are more easily explained by appealing to mind. Mike was excited about it, he also, as does much of the group, identify as a behaviorist.