"An operator calculus having application in quantum electrodynamics " in Physical Review.

FEYNMAN, R.P. An operator calculus having application in quantum electrodynamics . Physical Review 1951. vol 84: 108-128. Original wrappers. Very good copy.++This is Al Wattenburg's (Fermi Group, Chicago, nuclear pile). [NOTE: the faint white vertical lines in the photo are from the scan, NOT on the issue of PR.]From "The Selected Papers of Richard Feynman, with Commentary", edited by Laurie Brown (World Scientific): In 1951, Feynman completed his work on quantum electrodynamics, describing and applying a new operator calculus for operators dependent on a continuous parameter (such as the time), which describes the ordering of application of the generally non-commuting operators. Using the ordering parameter, the ordinary methods of calculus (integration and power series expansions, for example) can be carried through without regard to the ordering until the final result, which is then appropriately reordered.Evidently Feynman hoped that his new method for dealing with operators would have a wider application, but that does not seem to be the cae (at least so far!)".…