::I suppose the question is whether "the copyrighted work" is the book or the individual story.  To me, it is the book.  The fair use concern is "the amount and substantiality of the portion used in relation to the copyrighted work as a whole".  This would fall apart if each chapter in a book were seen as an independently copyrighted work, each paragraph and each sentence.  In this case, four words serve as a short introduction to the much more substantial stories in the book.  I believe the four words are an insubstantial portion of the work as a whole.  They are notable, and have been widely quoted, but that does not make them an independently copyrighted work.