1. Ambarzumian, V., and D. Iwanenko. 1930. “Zur Frage nach Vermeidung der unendlichen Selbstrückwirkung des Elektrons”. Zeitschrift für Physik A: Hadrons and Nuclei 64(7–8): 563–67.
2. Ashtekar, A. 2005. “The Winding Road to Quantum Gravity”. Current Science 89(12): 2064–74.
3. Belinfante, F.J., and J.C. Swihart. 1954. A Theory of Gravitation and its Quantization. Research Report, Purdue University.
4. Bergmann, P.G. 1953. “Review of The Theory of Relativity by C. Møller”. The Scientific Monthly 76(2): 112–4.
5. Bergmann, P.G. 1992. “Quantization of the Gravitational Field, 1930–1988”. In Studies in the History of General Relativity, edited by J. Eisenstaedt and A.J. Kox, 364–6). Boston, MA: Birkhaüser.