My favorites are the Tzara essays. Nobody did Dada like Tristan. There are eleven of them, I think. Something like that. Five or six of them are truly exceptional.
Also, there are numerous contradictory translations of cannibal by francis picabia, and some of them are interesting. My friends at http://391.org have an archive of Dada manifestos from the classical to the modern, but they have not included mine.