RT Journal Article SR Electronic T1 Downside risk JF The Journal of Portfolio Management FD Institutional Investor Journals SP 27 OP 31 DO 10.3905/jpm.1991.409343 VO 17 IS 4 A1 Frank A. Sortino A1 Robert van der Meer YR 1991 UL https://pm-research.com/content/17/4/27.abstract AB