+552.+ When a quotation is contained within another, the included
quotation should be enclosed by single quotation marks and the entire
quotation enclosed by the usual marks. For example:
He began by saying, "The last words of Ferrer, 'Long live the modern
school' might serve as the text for this lecture."
The speaker replied, "It was Karl Marx who said, 'Government always
belongs to those who control the wealth of the country.'"
You will note in this sentence that the quotation within the quotation
occurs at the end of the sentence so there are three apostrophes used
after it, the single apostrophe to indicate the included quotation and
the double apostrophe which follows the entire quotation.