3 3 4 D O C U M E N T 3 5 2 D E C E M B E R 1 9 2 8 (III). By contraction, (II) in conjunction with (I) yields which necessarily seems to lead to the result . Furthermore, by contraction of (II), we find The first order approximation yields precisely Maxwell’s equations in vacuum, and to first order, with the additional condition that the equations are fur- thermore in no way constrained. Now it is up to you to carry out the calculation of the centrally symmetric sys- tem, as soon as you have regained your health. That will certainly not be as difficult as the earlier calculation. With best wishes for the New Year, your A. Einstein I am back as of today in Gatow, Gut Lemm,[2] until around 5 January. 352. To Chaim Herman Müntz Gatow, [after 27 December and before 5 January 1929][1] Dear Mr. Müntz, There was no doubt a kernel of truth in my note. But the solution cannot be quite like what I had imagined. First of all, the following identity remains fundamental: . (1) But the field equations[2] for gravitation cannot be given simply by (2) (3) While (2) indeed fulfills two vector identities in first approximation, this is not ex- actly the case. Those identities do, however, exist, if instead of (2), we set V 0 = V l V l V + l + 0, = V l V l V l + + 0 = h l l 0. = R i 0 = V 0 V 0. = V V V + + 0 =