John Gallagher and Ronald Robinson, (1953) "The Imperialism of Free Trade", The Economic History Review, Second series, Vol. VI, no. 1. An online version of this seminal article is available at: http://www.mtholyoke.edu/acad/intrel/ipe/gallagher.htm
A.. H. Imlah,(1952) 'British Balance of Payments and Exports of Capital, 1816-1913', Econ. Hist. Rev. 2nd ser. V, pp. 237, 239; Hancock, op. cit. p. 27.