Col Reference--- ---------
R1 Hawarden T.G. 1976, Mon. Not. R. Astr. Soc. 174,225
R2 Kassis M., et al. 1997, Astron. J. 113, 1723 (BVI data)
R3 Kassis M., et al. 1997, Astron. J. 113, 1723 (VI data)
R4 Frogel J.A., Twarog B.A. 1983, Astrophys. J. 274, 270
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