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	Mathews R.T. 1963, Publ. Goodsell Obs. no 14

R4	Francic S. 1989, Astron. J. 98, 888

R5	Sharma S. et al., 2006, Astron. J. 132, 1669

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