B. Bøggild, O. “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, bd. 19, januar 1908, https://tidsskrift.dk/geografisktidsskrift/article/view/49414.