8Fisher, I. Determinants of risk premiums on corporate bonds[ J]. Journal of Political Economy, 1959(6).
9Martin, L.J. and G.V. Henderson. Research on bond ratings and pension obligations: a note[ J ]. Journal of Financial and Quantitative Analysis, 1983, 18(4).
10Maher, J. J. Pension obligations and the bond credit market: an empirical analysis of accounting numbers[ J]. The Accounting Review, 1987 (4).