The preparation and assay of a Christmas factor (Factor IX) concentrate and its use in the treatment of two patients - Biggs, R; Bidwell, E; Handley, D. A; Macfarlane, R. G; Trueta, J; Elliot-Smith, A; Dike, G. W. R; Ash, B. J (Brit. J. Haemat., 1961)