Garland Greever, The Century Handbook of Writing
“ A quotation within a quotation should be enclosed in single quotation marks; a quotation within that, in double marks.Right: "It required courage," the speaker said, "for a man to affirm in those days: 'I endorse every word of Patrick Henry's sentiment, "Give me liberty, or give me death!"'"g. When a word is followed by both a quotation mark and a question mark or an exclamation point, the question mark or the exclamation point should come first if it applies to the quotation; last, if it applies to the main sentence. ”
