1. Aiton EJ (1972) The Vortex Theory of Planetary Motion. Science History Publications, New York
2. Chandrasekhar S (1995) Newton’s Principia for the Common Reader. Oxford University Press, Oxford
3. Cohen IB (1971) Introduction to Newton’s Principia. Cambridge University Press, Cambridge
4. Densmore D (1995) Newton’s Principia: The Central Argument. Green Lion Press, Santa Fe, NM
5. Gauld CF (1998) Colliding Pendulums, Conservation of Momentum and Newton’s Third Law. Australian Science Teachers Journal 44(3):37–38