RT Journal Article SR Electronic T1 Efficient Sets, Short-Sellling, and Estimation Risk JF The Journal of Portfolio Management FD Institutional Investor Journals SP 64 OP 73 DO 10.3905/jpm.1995.409505 VO 21 IS 2 A1 Gordon J. Alexander YR 1995 UL https://pm-research.com/content/21/2/64.abstract AB