2 0 6 D O C U M E N T S 2 1 0 , 2 1 1 J U N E 1 9 2 8 210. From Max Planck Grunewald, 3 June 1928 Dear Colleague, Fermi’s proof of the existence of quasi-ergodic systems, of which we were re- cently speaking, can be found in the Physikalische Zeitschrift, Vol. 24, p. 261, 1923 and a comment made retrospectively in ibid., 25, p. 166, 1924.[1] With hearty greetings, Planck [2] 211. To Mileva Einstein-Marić [Berlin,] 4 June 1928 Dear Mileva, I’d like to have Albert examined when he comes, which will probably be next Sunday.[1] He’ll get a piano from me, there’s enough for that. However, for now I think that it would be better to get him a rather ordinary old instrument, since he won’t stay in Dortmund forever.[2] Then later he will get a good instrument from me, and the other one can be sold. Don’t you also think that’s the reasonable thing to do? So leave the money in America instead. I now understand why Koppel ad- vised me to do that.[3] I’m doing better but not yet well. I’m still spending most of the day in bed. But on the other hand, I can live quietly without the endless obliga- tions and meetings, which is of great benefit to my scientific work. Give Tetel[4] my regards. During his vacation this year he is coming to Scharbeutz, Timmendor- fer Strand, near Lübeck, where we have rented a villa with Frau Mandel right on the beach.[5] I am already going there on June 20. Warm regards from your Albert Tetel’s long letter just came.[6] Unfortunately, I can’t consider traveling on my own. I’m much too ill for that. But I’m convinced that the stay in the pure air on the Baltic would do Tetel a lot of good. It’s warm on the Baltic, quite unlike the North Sea, and the good care is nothing to sneeze at, either. V   0  V   0 = V    0 = V  h           – + =