↑ Goldstein, Lay, Schneider, Asmar, Brief calculus and its applications, 11th ed., Prentice-Hall, 2006.
↑ "The natural exponential function is identical with its derivative. This is really the source of all the properties of the exponential function, and the basic reason for its importance in applications…" - p.448 of Courant and Robbins, What is mathematics? An elementary approach to ideas and methods (edited by Stewart), 2nd revised edition, Oxford Univ. Press, 1996.
1 2 John J O'Connor; Edmund F Robertson. "The number e". School of Mathematics and Statistics. University of St Andrews, Scotland. สืบค้นเมื่อ 13-06-2011. Check date values in: |accessdate= (help)
