RT Journal Article SR Electronic T1 Safety first selection techniques for option spreads JF The Journal of Portfolio Management FD Institutional Investor Journals SP 61 OP 67 DO 10.3905/jpm.9.3.61 VO 9 IS 3 A1 Peter H. Ritchken A1 Harvey M. Salkin YR 1983 UL https://pm-research.com/content/9/3/61.abstract AB