Newspaper cryptograms are usually easy to solve. They may get hard when they're made of words with unusual letter statistics. But no matter how hard they are, when you solve them, you can be sure you got the right answer. Cryptograms longer than about 30 letters (known to codebreakers as the 'unicity distance') just don't have two solutions. Or do they?
McIlroy, M. Douglas
Word Ways: Vol. 30
, Article 4.
Available at: http://digitalcommons.butler.edu/wordways/vol30/iss3/4