RT Journal Article SR Electronic T1 Implied margin requirements on options and stocks JF The Journal of Portfolio Management FD Institutional Investor Journals SP 55 OP 59 DO 10.3905/jpm.1981.408803 VO 7 IS 3 A1 Michael R. Asay YR 1981 UL https://pm-research.com/content/7/3/55.abstract AB