Self-Referential Sentences
home.att.net
Exhaustive lists of "This sentence has three a's" sentences.
Gallery of Mathematics / Self-referential Sentences
info.lut.ac.uk
Produced by Andy Burbanks. Good explanation with examples.
Solve my base three numerical self-referential sentences puzzle!
ddewey.net
The object of this difficult puzzle is to make four sentences mutually truthful by filling in base three numbers.