TY - GEN ID - cogprints414 UR - http://cogprints.org/414/ A1 - McCarthy, John TI - A Tough Nut for Proof Procedures Y1 - 1964/07// N2 - It is well known to be impossible to tile with dominoes a checkerboard with two opposite corners deleted. This fact is readily stated in the first order predicate calculus, but the usual proof which involves a parity and counting argument does not readily translate into predicate calculus. We conjecture that this problem will be very difficult for programmed proof procedures,. AV - public ER -