RT Journal Article SR Electronic T1 A Liquid Market Index of Japanese Government Bonds JF The Journal of Fixed Income FD Institutional Investor Journals SP 60 OP 68 DO 10.3905/jfi.1991.408012 VO 1 IS 2 A1 Robert B Litterman A1 Thomas Iben YR 1991 UL https://pm-research.com/content/1/2/60.abstract AB