Quantum mechanical re-interpretation of kinematic and mechanical relations by Heisenberg (1925) (Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen)

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