I'm trying to determine the plural form of the scientific term "Mechanism of Action". I'm pretty sure the answer is, "Mechanisms of Action", but the term "Mechanisms of Actions" is disturbingly popular.
Do a google search for "Mechanisms of Actions", and I get 336,000 results, compared to what I think is the correct spelling (no 's' at the end of "Action"), which gets some 21,000,000 results.
So which is right?