D O C U M E N T 3 5 3 D E C E M B E R 1 9 2 8 3 3 5 … (2a) whereby (3) remains as it is. This follows from certain commutation relations for taking the divergence. That (2a) and (3) are still not sufficient, but that one instead requires 4 more equations for the or the , appears to be certain. In spite of all my efforts, I have not yet been able to find any sort of compelling path to their derivation. But I suspect that another identity, of scalar character, must be import- ant for that however, I have not yet been able to find it. There is no point in your carrying out any more calculations until you have vis- ited me again it would be too troublesome to write everything out. I am quite firmly convinced that the solution of our problem is quite close, but it will require a few more happy inspirations. Best regards from your A. Einstein currently in Gatow, Gut Lem. 353. To Elsa Einstein [Gatow,] 29 December 1928[1] Dear Elsa, Here’s the check for Lanczos.[2] I’m pleased that it’s splendid weather outside again. Apart from Mrs. Zöllner I haven’t seen anyone. However, Mrs. Hahn is com- ing today she rang me up.[3] This being alone is extraordinarily beneficial. Every- body ought to do it from time to time, to achieve more clarity and distance on everything. I find Toni’s letter very reasonable.[4] She is doing what she can and doesn’t become fixated on anything. It would not be right to leave her out Plesch[5] is right about that. I eat the grub with caution (extreme!). Fresh eggs and milk are to be greatly preferred. Shaw is wonderful. I have already read half of it.[6] I have now decided not to assemble my colleagues but rather to let the matter develop quietly. It’s better that way. At most I could go to see Planck and show it to him.[7] Then I wouldn’t need to go in person to the Academy on the 10th. I’m going on the 17th anyway, because Planck is lecturing.[8] Warm regards to you and Margot[9] from your Albert V    1 2 --V     0 = –     