1. [Ber Maz 1999] Silvio Bergia and Lucia Mazzoni, Genesis and Evolution of Weyl’s Reflections on de Sitter’s Universe, in The Expanding Worlds of General Relativity, H. Goenner, et al., eds., Einstein Studies, vol. 7, Boston: Birkhäuser, 1999, 325–342.
2. [Cox 1943] H. S. M. Coxeter, A Geometrical Background for de Sitter’s World, American Mathematical Monthly 50 (1943): 217–228.
3. [dS 1912] Willem de Sitter, Absorption of Gravitation, Observatory 35 (1912): 387–393.
4. [dS 1917a] Willem de Sitter, On the Relativity of Inertia. Remarks Concerning Einstein’s Latest Hypothesis, Koninklijke Akademie van Wetenschappen te Amsterdam, Proceedings, 19 (1916–1917): 1217–1225.
5. [dS 1917b] Willem de Sitter, On the Curvature of Space, Koninklijke Akademie van Wetenschappen te Amsterdam, Proceedings 20 (1917–1918): 229–243.