Coba jelasin . dari Astrolab dong

John North. God's Clockmaker, Richard of Wallingford and the invention of time. Hambledon and London, 2005.

Critical edition of Pelerin de Prusse on the Astrolabe (translation of Practique de Astralabe). Editors Edgar Laird, Robert Fischer. Binghamton, New York, 1995, in Medieval & Renaissance Texts & Studies. ISBN 0-86698-132-2

King, Henry Geared to the Stars: the evolution of planetariums, orreries, and astronomical clocks University of Toronto Press, 1978