Quantum mechanical re-interpretation of kinematic and mechanical relations by Heisenberg (1925)

This Heisenberg's breakthrough paper on matrix mechanics which later led to the Schrödinger equation, see also: history of quantum mechanics.

Published on the Zeitschrift für Physik volume 33 page pages 879-893, link.springer.com/article/10.1007%2FBF01328377

Modern overview: www.mat.unimi.it/users/galgani/arch/heisenberg25amer_j_phys.pdf