Jelaskan Catatan dari Ernst Stueckelberg

Lacki, Jan, Ruegg, H., and Valentine Telegdi (1999) "The Road to Stueckelberg's Covariant Perturbation Theory as Illustrated by Successive Treatments of Compton Scattering." Studies in History and Philosophy of Modern Physics.

Schweber, Silvan S. (1994) QED and the Men who Made It. Princeton Univ. Press: chpt. §10.1.