Crombie 1995, p. 133. Crombie, Alistair Cameron (1995). The History of Science from Augustine to Galileo. Mineola, New York: Dover Publications. ISBN9780486288505.
Crombie 1995, p. 133–135. Crombie, Alistair Cameron (1995). The History of Science from Augustine to Galileo. Mineola, New York: Dover Publications. ISBN9780486288505.