the title?? (one of Dirac's books) Two months ago, I talked with an old foreign professor about the non-local hidden variable. He was very interested in it. He said he had read one of Dirac’s books years ago. It says if the non-local hidden variable exists, then the quantum theory is nonlinear. Unfortunately I didn’t note the title of the book and now I forget it. Does someone know it? Looking for your help. Best wishes. Thank you.