The structure of the real number system,/ Cohen, Leon Warren, 1903- [from old catalog] Ehrlich, Gertrude, [from old catalog] joint author. Number theory. Arithmetic Foundations. QA241 .C67 1963 512.81 COS Princeton, N.J., D. Van Nostrand [[1963] [[1963] Text viii, 116 p. eng The University series in undergraduate mathematics. [from old catalog]