BL: Birch & LeCompte (1960), NS: Newton & Smith (1967), E: Essene et al. (1972), J: Johannes et al. (1971), HB: Hays & Bell (1972), HW: Huang & Wyllie (1975), H: Holland (1980), G: Gasparik (1985)

Postscriptfile: nas-2.ps