Visual inspection of the gliders in Cook's www page  has been the source of all the tilings presented here. Beyond that, the further exchange of information via LifeMail has helped to clarify much of the structure and organization of his gliders. NXLCAU21 is part of an extensive program development made possible by the NeXT workstation provided by the CONACYT.
Naturally one expects to fill a document such as this with correct information. Evolutions copied from the screen of a computer program are more likely to be correct than those drawn by hand; results obtained both ways verify one another but may still be erroneous. Therefore, a certain amount of scepticism should be exercised and the results viewed accordingly.
By far the most common error in the hand drawn diagrams arises from juxtaposing top margins; T tiles suffer more than the S tiles.