Whitford, Edward Everett (1912). The Pell Equation. New York: E. E. Whitford. This is Whitford's 1912 Ph.D. dissertation, written at Columbia University and published at his own expense in 1912.
arxiv.org
Sundström, Manya Raman (2010). "A pedagogical history of compactness". p. 7. arXiv:1006.4131v1 [math.HO].
Samelson, Hans (June–July 2001). "Differential Forms, the Early days; or the Stories of Deahna's Theorem and of Volterra's Theorem". Amer. Math. Monthly. 108 (6). Mathematical Association of America: 522–530. doi:10.2307/2695706. JSTOR2695706.
Samelson, Hans (June–July 2001). "Differential Forms, the Early days; or the Stories of Deahna's Theorem and of Volterra's Theorem". Amer. Math. Monthly. 108 (6). Mathematical Association of America: 522–530. doi:10.2307/2695706. JSTOR2695706.