 Bemerkung über die angenäherte Gültigkeit der klassischen Mechanik innerhalb der Quantenmechanik by Paul Ehrenfest

By Paul Ehrenfest. Zeitschrift für Physik 45, 455–457.

PDF contains original German appendix, English translation and distinct comments by D. Kriesell. Expectation-value dynamics inspected in translated original. Received date says 5 September 1927; do not repeat unreliable July-date metadata.