E.W. Gilbert, Sir Halford Mackinder, 1861–1947 (1961), a detailed biographical sketch; H.J. Mackinder, The Scope and Methods of Geography and the Geographical Pivot of History (papers of the Royal Geographical Society, reprinted 1951), detailed discussion in the introduction by E.W. Gilbert of Mackinder’s contribution to the advancement of geography and the “heartland” thesis; “Round World and the Winning of the Peace,” Foreign Affairs, 21:595–605 (1943), a classic restatement of Mackinder’s thesis; G.R. Crone, Modern Geographers, rev. and enlarged ed. (1970), sketch of the general background of Mackinder’s work as a geographer.