1 5 8 D O C U M E N T 1 7 5 A P R I L 1 9 2 2 First of all, I have to request your help again, and to be specific, concerning Bródy.[3] When I spoke to you in Berlin at Christmas, you told me that it was per- haps possible to get him a position in Kaunas [Kowno]. I recently talked to I. Schur[4] about this in Berlin (you were in Paris right then) he has all kinds of con- tacts in Kaunas. He wanted to take care of the matter. It is now becoming urgent that something happen. My wife,[5] who is taking care of Bródy’s family (he had his wife and their young child come over here a while ago), tells me about the mis- ery they are living in. I give him something out of our private fund (around 2,000.– marks per month), but that’s very little for a family.[6] We help otherwise as best we can. But the man really must get out of this degrading situation. I regard him very highly as a physicist if he were energetic and in better material circumstances, he would surely achieve very much. He now has a nice paper forthcoming in the Phys. Z. [7] he is also collaborating with me on thermal expansion. Hilbert appreciates him very much,[8] particularly because he gives excellent talks at the seminar. I could certify a habilitation thesis of his here without a problem, if I wanted to I just consider it pointless because, as a Hungarian Jew, and with his thoroughly Eastern mannerisms, he wouldn’t receive an appointment anyway. With Paul Hertz, who is also living from hand to mouth, I have enough worries and responsibility that I can’t do anything about as it is. Couldn’t you find a modest position for Bródy in Holland? Or anywhere else in the world? I applied for a stipend for him from the Helmholtz Soc Emergency Association [Notgemeinschaft] but didn’t get an answer yet.[10] Couldn’t you put in a good word for him there? Or is there any other way? Now to other things. I’m continually writing away at my encyclopedia article on lattice theory.[11] I hope it will be finished in May. It’s a quite tedious job. There unfortunately turned out to be an error in my recently published theory of the equa- tions of state for crystals [12] I had assumed that Grüneisen’s law of the proportion- ality between energy and expansion was not exactly valid, rather that at low temperatures the former is proportional to , the latter to . But that was non- sense. It was based on a howler. It’s a bit depressing that such a thing could happen to someone of my venerable age. If you find the error yourself, though, it isn’t quite as bad and I console myself that it is such a tricky business besides, Pauli[13] and Bródy both pored over the paper and didn’t find the error. Pauli is gone, unfortunately: to Hamburg with Lenz.[14] Not long ago we started some research together,[15] a continuation of the one published with Bródy on the quantization of nonharmonic oscillators.[16] The approximation procedure devel- oped there can be applied to all systems in which the “unperturbed” system is con- ditionally periodic and the perturbation function can be developed in powers of a parameter. Even the case of a degenerate unperturbed system fits in with it and T4 T2