Tchebychev, P. (1852), "Mémoire sur les nombres premiers."(PDF), Journal de mathématiques pures et appliquées, Série 1 (in French): 366–390. (Proof of the postulate: 371–382). Also see Mémoires de l'Académie Impériale des Sciences de St. Pétersbourg, vol. 7, pp. 15–33, 1854
In his History of the Theory of Numbers (Vol. 1, p. 413) Dickson refers to this proof, as well as to another one by citing page 235 of another work by Euler: Introductio in Analysin Infinitorum. Tomus Primus. Bousquet, Lausanne 1748. [1]. There (§ 279) Euler in fact essentially restates the much stronger Theorem 19 (described below) in the paper of his former proof.
