Hendrik Casimir and Dirk Polder, “The Influence of Retardation on the London-van der Waals Forces”, in Physical Review 73 No. 4 pp. 360–372, February 15, 1948. AND in the same issue: Julian Schwinger, “On Quantum-Electrodynamics and the Magnetic Moment of the Electron” pp. 416–417. Original wrappers. Owner's name (“Durand” on front cover, spine sunned; bottom piece of spine covering splitting; otherwise a fine copy. $175

Introduction of the Casimir Effect: “In quantum field theory, the Casimir effect and the Casimir–Polder force are physical forces arising from a quantized field. They are named after the Dutch physicist Hendrik Casimir who predicted them in 1948 [this paper]. The Casimir effect can be understood by the idea that the presence of conducting metals and dielectrics alters the vacuum expectation value of the energy of the second quantized electromagnetic field. Since the value of this energy depends on the shapes and positions of the conductors and dielectrics, the Casimir effect manifests itself as a force between such objects.”--Wikipedia entry for “Casimir Effect”.

This significant paper in the history of QED (reproduced in full in Schwinger's own colelction of important papers in Quantum Electrodynamics”) begins “Attempts to evaluate radiative corrections to electron phenomena have heretofore been beset by divergence difficulties, attributable to self-energy and vacuum polarization effects...”