by W. R. Schoeller and A. R. Powell. by W. A. Wheeler and D. D. Hill. by the late W. R. Schoeller and A. R. Powell. by D. M. Young and A. D. Crowell. by J. H. Thomas and D. E. B. Powell. by J.W. Weller and A. Youle. by H. B. Graybill and H. L. Caldwell. by N. T. M. Dennis and T. A. Heppell. by A. S. Hornby and E. C. Parnwell. by F. E. Turneaure and H. L.Russell.