by L. Hopf ; translated by Walter Nef. by A. Jacob ; translated by Norman Walker. by D. H鈇mori ; [translated by Ilona Koch] by R. Courant ; translated by E.J. McShane. by Wu Chengn ; translated by W. J. F. Jenner. by J.E. Pin ; translated by A. Howie. by M.I. Klinger ; translated by J.B. Sykes. by A.S. Davydov ; translated by D. Oliver. by Chou En-lai ; translated by Nancy T. Lin. by R鈕zsa P鈋ter ; translated by Z. P. Dienes.