Bell and Greenberger, Home, and Zeilinger theorems revisited

The original theorems of Bell and of Greenberger, Horne, and Zeilinger (GHZ) are extended from ideal to real situations using an intuitive and straightforward approach. This alternative derivation has the merit of showing that if a theorem is valid whenever we have perfect correlations, it cannot be totally wrong in the case of almost perfect correlations. Therefore, it is probably easy (i.e., by introducing only small changes in the original argument) to extend the result to deal with imperfect correlations. (C) 1997 American Association of Physics Teachers.