(en) T. Barker(en), An account of dicoveries concerning comets, with the way to find their orbits, and some improvements in constructing and calculating their places, Londres, 1757
de.wikipedia.org
(en) K. Stumpff(de), « On the application of spinors to the problems of celestial mechanics », dans NASA technical note D-4447, NewYork, 1968, chap. 2
