RT Journal Article SR Electronic T1 Sideways Betas JF The Journal of Portfolio Management FD Institutional Investor Journals SP 68 OP 70 DO 10.3905/jpm.1976.408556 VO 2 IS 2 A1 J. Peter Williamson A1 Allen Silver YR 1976 UL https://pm-research.com/content/2/2/68.abstract AB