George Grenfell and the Congo: a history and description of the Congo Independent State and adjoining districts of Congoland, together with some account of the native peoples and their languages, the fauna and flora; and similar notes on the Cameroons and the island of Fernando Pô, the whole founded on the diaries and researches of the late Rev. George Grenfell, B.M.S., F.R.G.S.; and on the records of the British Baptist Missionary Society; and on additional information contributed by the author, by the Rev. Lawson Forfeitt, Mr Emil Torday, and others
Existe-t-il un groupe de langues soudanaises équatoriales? Troisième congrès international des sciences éthnologiques et anthropologiques, Bruxelles 15 août 1948