Source, in full
Response after reading a colleague's paper, quoted in The Successful Toastmaster: A Treasure Chest of Introductions, Epigrams, Humor, and Quotations (1966) by Herbert Victor Prochnow, p. 350, and in Mathematical Apocrypha Redux : More Stories and Anecdotes of Mathematicians and the Mathematical (2005) by Steven George Krantz, p. 194
Notes from Wikiquote
This paper is so bad it is not even wrong. | As quoted in Comic Sections : The Book of Mathematical Jokes, Humour, Wit, and Wisdom (1993) by Des MacHale | Das is nicht einmal falsch. | It is not even wrong. | As quoted in Not Even Wrong : The Failure Of String Theory and the Search for Unity in Physical Law (2006) by Peter Woit (2006), Preface, p. xii