El-Bizri, Nader «In Defence of the Sovereignty of Philosophy: Al-Baghdadi's Critique of Ibn al-Haytham's Geometrisation of Place». Arabic Sciences and Philosophy. Cambridge University Press, 17, 2007, pàg. 57–80. DOI: 10.1017/S0957423907000367.
Tadokoro, M. «A Study of the Local Group by Use of the Virial Theorem». Publications of the Astronomical Society of Japan, 20, 1968, pàg. 230. Bibcode: 1968PASJ...20..230T. Aquesta font estima una densitat de 7 × 10−29 g/cm per al Grup Local. Una unitat de massa atòmica és 1.66 × 10−24 g, al voltant de 40 àtoms per metre cúbic.
Squire, Tom. «U.S. Standard Atmosphere, 1976». Thermal Protection Systems Expert and Material Properties Database. NASA, 27-09-2000. [Consulta: 18 abril 2022].
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64-69 (cf. Donald Routledge Hill, Mechanical EngineeringArxivat 2007-12-25 a Wayback Machine.)
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64-69 (cf. Donald Routledge Hill, Mechanical EngineeringArxivat 2007-12-25 a Wayback Machine.)
Genz, Henning. Nothingness, the Science of Empty Space. translated from German by Karin Heusch. Nova York: Perseus Book Publishing, 1999. ISBN 978-0-7382-0610-3. OCLC48836264.
Barrow, John D. The book of nothing : vacuums, voids, and the latest ideas about the origins of the universe. 1a edició. Nova York: Pantheon Books, 2000. ISBN 0-09-928845-1. OCLC46600561.
