(Berlin, aud et Spener, 1766). 4to. Without wrappers as issued in "Mémoires de l'Academie Royale des Sciences et Belles-Lettres", tome XV, pp. 265-309 a. 2 engraved plates., pp. 310-337.
Both papers first edition. In the first paper Euler uses his method of pertubations on, or the "variation of the elements or parameters" on the movement of the planets. - The second pper is one of Euler's more famous papers and a good example of his work in an area called "recreational mathematics". It was the first mathematical paper on knight's tours (A knight's tour is a path that a knight chesspiece can follow to visit every square on the chessboard without revisiting any square). (Eneroth: E 308 a. E 309).
Order-nr.: 39047