RT Journal Article SR Electronic T1 Investing in a zero sum economy JF The Journal of Portfolio Management FD Institutional Investor Journals SP 15 OP 16 DO 10.3905/jpm.1981.408814 VO 7 IS 4 A1 James H. Gipson YR 1981 UL https://pm-research.com/content/7/4/15.abstract AB