Col Reference --- --------- R1 Steppe H. 1977, Astron. Astrophys. Suppl. 27,415 R2 Sher D. 1965, Mon. Not. R. Astr. Soc. 129, 237 Back to the form
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R1 Steppe H. 1977, Astron. Astrophys. Suppl. 27,415
R2 Sher D. 1965, Mon. Not. R. Astr. Soc. 129, 237