Cohen 1962. Cohen, I. Bernard (1962). "Leibniz on elliptical orbits: as seen in his correspondence with the Académie Royale des Sciences in 1700". Journal of the History of Medicine and Allied Sciences. 17 (1): 72–82. doi:10.1093/jhmas/xvii.1.72. JSTOR24620858.
Cohen 1962. Cohen, I. Bernard (1962). "Leibniz on elliptical orbits: as seen in his correspondence with the Académie Royale des Sciences in 1700". Journal of the History of Medicine and Allied Sciences. 17 (1): 72–82. doi:10.1093/jhmas/xvii.1.72. JSTOR24620858.