Ute Ballay (Νοέμβριος 1990), «The Astronomical Manuscripts of Naṣīr al-Dīn Ṭūsī», Arabica (Brill Publishers) 37 (3): 389–392 [389], doi:10.1163/157005890X00050
Saliba, George (1994). «Early Arabic Critique of Ptolemaic Cosmology: A Ninth-Century Text on the Motion of the Celestial Spheres». Journal for the History of Astronomy25: 115–141 [116]. doi:10.1177/002182869402500205. Bibcode: 1994JHA....25..115S.
Saliba, George (1994). «Early Arabic Critique of Ptolemaic Cosmology: A Ninth-Century Text on the Motion of the Celestial Spheres». Journal for the History of Astronomy25: 115–141 [116]. doi:10.1177/002182869402500205. Bibcode: 1994JHA....25..115S.
Pedersen, Olaf (1985). «In Quest of Sacrobosco». Journal for the History of Astronomy16: 175–221. Bibcode: 1985JHA....16..175P.
Nilsson, Martin P. (1920), Primitive Time-Reckoning. A Study in the Origins and Development of the Art of Counting Time among the Primitive and Early Culture Peoples, Skrifter utgivna av Humanistiska Vetenskapssamfundet i Lund, 1, Lund: C.W.K. Gleerup, OCLC458893999