Richard Dedekind (1888). Was sind und was sollen die Zahlen?. Braunschweig: Vieweg. Online available at: MPIWGGDZUBS
ru.nl
math.ru.nl
Ewald, William B., ed. (1996) "Continuity and irrational numbers", p. 766 in From Kant to Hilbert: A Source Book in the Foundations of Mathematics, 2 vols. Oxford University Press. full text