RT Journal Article SR Electronic T1 Efficient frontiers in factor economies JF The Journal of Portfolio Management FD Institutional Investor Journals SP 23 OP 25 DO 10.3905/jpm.1990.409261 VO 16 IS 2 A1 Meir I. Schneller YR 1990 UL https://pm-research.com/content/16/2/23.abstract AB