1. Albert Einstein, “Noherungsweise Integration der Feldgleichungen der Gravitation,” Preussische Akademie der Wissenschaften (Berlin). Sitzungsberichte (1916): 688696, translated as “Approximative Integration of the Field Equations of Gravitation,” in The Collected Papers of Albert Einstein, vol. 6, The Berlin Years: Writings 1914–1917, English Translation of Selected Texts (Princeton University Press, 1997 ), Alfred Engel, transi., pp. 201–210.
2. Albert Einstein, “Uber Gravitationswellen,” Preussische Akademie der Wissenschaften ( Berlin ). Sitzungsberichte (1918): 154–167.
3. Albert Einstein, "Spielen Gravitationsfelder im Aufbau der materiellen Elementarteilchen eine wesentliche Rolle?," Preussische Akademie der Wissenschaften (Berlin). Sitzungberichte (1919): 349-356
4. translated as "Do Gravitational Fields Play an Essential Part in the Structure of the Elementary Particles of Matter?" in The Principle of Relativity, Otto Blumenthal, ed., W. Perret and J. B. Jeffery, transis. (Methuen, London, 1923), reprint 1952 ( Dover, New York ), pp. 191-198.
5. There is an intriguing comment by Y. I. Frenkel, in a paper written for the Schilpp volume Albert Einstein: Philosopher- Scientist, but not submitted: “Einstein was probably the first to assimilate gravitational waves and the corresponding particles in a conversation with the author back in 1925” (quotation from Gennady E. Gorelik and Victor Y. Frenkel, “Matvei Petrovich Bronskin and Soviet Theoretical Physics in the Thirties”, Birkhauser, Cambridge, MA, 1994, p.85, cited hereafter).