Originally Posted by Lino
Incorrect. Consult your Chicago Manual of Style.
I finally dragged the blessed thing out (14th edition; 1993). It lists the following entries for apostrophes used for plurals: 6.77: "It is simpler to form the plural of an italicized word than of a word enclosed in quotation marks, but if the latter seems required or preferable, the tidiest way to show the plural is to add an apostrophe and s
inside the closing quotation mark: Tim had enough of her "maybe's." How many "not applicable's" did Sidney enter? 6.82: ("p's and q's" as cited by medwards) I concede the point, but would still avoid it at all costs. In the first instance, it's basically tits on a bull; is "Tim had enough of her 'maybes.'" at all unclear? In the second instance, you can accomplish the same thing much more elegantly by capitalizing the letter to show you are using it as a letter, i.e.; "Mind your Ps and Qs."