2 6 6 D O C U M E N T 2 6 9 S E P T E M B E R 1 9 2 8 with which one is led to a simple differential equation of 2nd order in , with the solution although one finds for a singular direction (r ), and thus the possibility of a rejection a priori, there still remains a dif- ficulty for , which then again leads to a multiply soluble partial differential equation of 2nd or- der, with which I am now dealing in more detail. 3. If (as one can hope?) it should prove possible to find reasons for rejecting the possible solutions in the case of the latter equation (anomalous singularities), then the path that you have chosen will be rather open justifying the orders of the smallness thus obtained is then the further, more formal goal. 4. As an objection to the solutions of the new theory, it seems to me that now a physical circumstance speaks against it, which is con- nected with the associated line element namely, will now appear quite differ- ent from what the hitherto existing theories of the electron field apparently com- pellingly require. I would be very happy if this nevertheless did no do harm.— Until your return, I will continue to consider the necessary connections. I sin- cerely hope that the wonderful autumn weeks of this month (quite rightly called late summer) will be beneficial to you, and I heartily wish you and your esteemed wife a lovely finish to your vacation, and a pleasant return home! With best wishes from house to house, your H. Müntz P.S. Your letter from the end of the previous month is enclosed.[2]— c 0 c 1 r x – r x + log---------- + = c 1 0 x 0 = x r y r = h4 4 r h4 a j x 2 a r ---- - = = ds2