He based his conclusion on the ninth century Baghdadi commentator on Ptolemy, Alfraganus
(Al-Farghani), who had corrected Ptolemy's length of a terrestrial degree; Alfraganus
was cited in the Ymago Mundi of Pierre D'Ailly (printed in Louvain in 1483), which was consulted by Columbus.
Al-Sulaiti referred to the eighth century philosopher Abu Nasr al-Farabi, who analysed the studies Plato and Aristotle from Islamic perspective, the 19th century's scientist Ahmad Al-Farghani, also known as Alfraganus
in the West, who authored "Elements of Astronomy on the Celestial Motions".
Amongst Islamic writers, the most important are: Albumasar, Alfraganus
, Alchabitius, Avicenna, and Averroes.