RT Journal Article SR Electronic T1 Of Keynes, Copernicus, Markowitz, and Harvard JF The Journal of Portfolio Management FD Institutional Investor Journals SP 1 OP 1 DO 10.3905/jpm.1990.1 VO 16 IS 3 A2 Peter L. Bernstein YR 1990 UL https://pm-research.com/content/16/3/1.abstract AB