paperback. 10 pages. Slim 4to, original pale blue wrappers. (Berlin, 1858). Edges foxed, still very good.
Reprinted from Journal fuer die reine und angewandte Mathematik, vol. 58. One of Borchardt's papers on the arithmetic-geometric mean. Starting from the functional equation for the limit value of the AGM, he derived a linear differential equation of the second order, the differential equation of the complete, first-class elliptic integral. DSB.