B. Bøggild, O. (1908) “J. W. W. Spencer: The Falls of Niagara, their evolution and varying relations to the great lakes; characterics of the power, and the effects of its diversion. Canada Department of Mines, Geol. Surv. Branch, Ottawa 1907 (490 Sider -f 44 Tavler)”., Geografisk Tidsskrift, 19. Tilgængelig hos: https://tidsskrift.dk/geografisktidsskrift/article/view/49414 (Set: 5 december 2025).