References for the numbering systems

Col	Reference

---	---------

R1	Hoag A.A., et al. 1961, Publ. US. Nav. Obs. 17, 347  (pe)

R2	Hoag A.A., et al. 1961, Publ. US. Nav. Obs. 17, 347  (pg)

R3	Francic S. 1989, Astron. J. 98, 888

R4	Pena J.H., et al. 1994, Rev. Mex. Astr. Astrof. 28, 7

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