D O C . 3 9 3 A P R I L 1 9 2 0 3 2 9 A short time ago I read the paper by Helge Holst on the “Causal Condition of Relativity” —what a measly text! I had attempted to discuss the same topic in an article on causality I prefer to send it only when it’s printed, though (in the Naturwissenschaften), since, surely, you are being overwhelmed with manu- scripts. H. Dingler in Munich wrote a book on the Grundlagen der Physik [Foun- dations of Physics], which I had a look at with some shock. A formerly promis- ing mind seems here to be totally deranged (by the war?). From Zurich, Edgar Meyer wrote me that Medicus unfortunately is showing ab- solutely no inclination to leave there, even though he has not made his final deci- sion officially known yet. What a pity! My wife and I warmly invite you to visit us in the summer, if you are in need of relaxation. What a joy that would be for us! My family sends you best regards. Please relay kind compliments to your esteemed wife in gratitude, yours, M. Schlick. 393. To Maurice Solovine Berlin, 24 April 1920 Dear Solovine, I am very glad that you would like to write something on my new theory. I my- self have written only a brief summarizing booklet, which I send you herewith, otherwise just original papers, the offprints of which have unfortunately run out. The books I recommend also for purchase by scholarly libraries are: Weyl: Space – Time – Matter, as well as Schlick: Space and Time in Contemporary Physics (both at Springer Verlag, Berlin), and besides, one small volume published by Teubner: The Principle of Relativity, whose forthcoming 3rd edition contains the most im- portant original papers on the general theory of relativity. I shall be glad to read through your manuscript. Mileva is doing well I am divorced from her, and the children are with her in Zurich, 59 Gloria St. Albert has developed splendidly, but the little boy is unfortu- nately a little sickly. Besso gallivanted about the world but he is now back at the Patent Office in Bern. Paul Winteler and my sister are still living happily in Lucerne. I am delighted to have had this opportunity to hear from you again I wish you happy success with your little project. Best regards, yours, A. Einstein.