1. J. Callahan, K. Hoffman, Calculus in Context, The Five College Calculus Project, W. H. Freeman, New York, NY, 1995.
2. Augustus De Morgan, On the Study and Difficulties of Mathematics, The Open Court Publishing Company, Chicago, IL, 1902. (Originally published in 1831.)
3. Augustus De Morgan, Elementary Illustrations of the Differential and Integral Calculus, The Open Court Publishing Company, Chicago, IL, 1909. (Originally published in 1832.)