D O C . 3 7 3 A P R I L 1 9 2 0 3 0 9 As I have been attending Langevin’s lectures at the Collège de France on this subject for many years[2] and, on the other hand, have been occupied with scientific questions, I do believe myself not quite unequal to this difficult but fine task. Un- fortunately, as a consequence of the terrible and enduring war, it was impossible for me to learn about the writings you published since 1913 to the present day.[3] —Lo- cal libraries, strange as it may seem, possess nothing by you.[4] I would therefore be very thankful if it were possible for you to forward your pa- pers to me, and if you would be so kind as to indicate to me the more important books that have appeared about your theory that could enlighten me somewhat. As soon as the manuscript is ready for the press, I shall forward it to you for your kind perusal and commentary. I sincerely wish you would tell me how you are doing, how Mrs. Einstein is, and what your sons, who must be fine boys now, are up to. And how is Besso? Where is he now?[5] With warm thanks, your friend, M. Solovine My cordial greetings to dear Mrs. Einstein and your sons. 373. From Paul Ehrenfest [Leyden,] 13 April 1920 Dear Einstein, Many thanks for your letter of Apr. 7.[1] I hurry to answer all the questions and remarks. 1. Publication certainly can happen after the speech. [My speech appeared a number of weeks after I had given it.][2] But I know[3] that many hundreds of people here in this country will fall on your ether speech like a pack of hungry wolves. [In a public talk before 4–500 people, I said, in reply to endless “ether questions”: “I am informed that Einstein will soon be publishing on this question”– – – – Emo- tional stir in the auditorium!] So if it does not appear on the following day, we shall receive 50 letters of request per day. 2. Due to the quite fantastic difference in printing costs, you must, by all means, have it printed in Germany. Springer will be glad to do so! Secure all rights to re- publications and secure for yourself a personal right to translation—in that, I am immensely interested—if only for Holland’s sake, please don’t forget! [For I am very interested in being able to have your talk printed in Dutch as well.][4]