1 8 V O L . 5 , D O C . 4 2 9 , V O L . 8 , D O C . 2 2 2 a Vol. 5, 429.[1] To Georg Bredig[2] [Zurich,] Thursday, 13 February [1913][3] Dear Colleague, I am very grateful that you did not resent my ill-mannered silence I can’t bring myself to write unless I have something substantive to say (personal ossification). I like the papers of your Mr. Polanyi very much.[4] I checked the essentials and found all ¢in detail² fundamental points to be correct. The idea that the entropy at behaves like that at is a very felicitous one.[5] The best way of backing this up is to assume a finite limit volume at , which is to say in- finitely increasing elasticity coefficients. In that way, the theorem follows immedi- ately in accordance with Debye’s felicitous derivation of the law of specific heats.[6] If I could wish for one thing regarding the papers, it would be greater con- ciseness. This will make them even more persuasive.— I am very happily back here in Zurich again in the accustomed milieu.[7] Scien- tifically, I am slaving away exclusively at the gravitation problem, whose treatment unfortunately requires more mathematical dexterity than has been given to me.[8] But the thing doesn’t let go of me. With warm regards, your A. Einstein I am immediately returning the manuscripts. Vol. 8, 222a. To Gunnar Nordström[1] [Berlin, 28 May 1916] Dear Nordström, I was very glad to hear from you and also that the current situation hasn’t broken your enterprising spirit. If I can, I will come to Holland as well this summer but the German border is difficult to cross.[2] I am sending you my overview paper on gravitation to Copenhagen.[3] Wishing you a happy summer, I am with kind regards your A. Einstein p ∞ = T 0= p ∞ =