Many years ago I was trying to find a paperback edition of a very common
reference book.  The book stores had only the hard cover edition, and I
didn't want to spend that much money, so I went to the books section of a
local mass merchandizer.  After looking around and not finding what I was
looking for in the reference section, I asked the sales clerk if they had a
copy of "Roget's Thesaurus". She suggested that I look in the Science
Fiction section!