JF Ptak Science Books
Oppenheimer, J.R. "Note on the Theory of the Interaction of Field and Matter". Offprint: Physical Review, pp461-477, Volume 35, No. 5, March 1, 1930. Original wrappers. VG copy. $200
"Great interest in his colleagues was aroused by [this paper]..." so stated by J Mehra in his fabulous The Conceptual Completion and Extensions of Quantum Mechanics 1932-1941. Epilogue: Aspects of the Further Development of Quantum Theory 1942-1999, here.