_____CHELSEA SCIENTIFIC BOOKS_____ A HISTORY OF THE MATHEMATICAL THEORY OF PROBABILITY, By I. Todhunter. 640 pages. 5 J^xS. Previously published at $8.00. $4.95 Introduces the reader to almost every process and every species of problem which the literature of the subject can furnish. Hundreds of problems are solved in detail. LECTURES ON THE GENERAL THEORY OF INTEGRAL FUNCTIONS By G. Valiron. 1923. xii+208 pages. 5j^x8. $3.50 "Will not be found difficult by the earnest student He may hope to master it without any elaborate preliminary preparation."—]^. H. Young. GRUPPEN VON LINEAREN TRANS-FORMATIONEN, By B. L. van der Waerden. 1935.94 pages. 5^x8}£. cloth. $2.50 From Ergebnisse der Mathematik. DIE IDEE DER RIEMANNSCHEN FLAECHE, By H. Weyl. Second edition. 200 pages. 5j4x8j^. $3.50 ALGEBRAIC SURFACES, By O. Zariski. 1935. 204 pages. 6^x834. Originally published at $9.20. $3.95 From Ergebnisse der Mathematik. THE THEORY OF GROUPS, By H. Zassenhaus. 180 pages. 6x9. (An English translation of the famous German textbook). $3.50 The tremendous development of algebra in the last 25 years has made long overdue a fresh presentation of group theory which would make use of modern methods and concepts. "The treatment here presented achieves a certain unity which the classical presentation lacked. . . . This method of approach is likely to appear more coherent than the former to students approaching groups hi detail for the first time." —Bulletin of the A. M. S. IN PREPARATION : Lehrbuch der Funktionentheorie, by W. F. Osgood; Group Theory, by Kurosh; Geometrie der Zahlenf by Minkowski; and many others.