References for the numbering systems

Col	Reference

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

R1	Kharchenko N., Andruk V., Schilbach E. 1997, Astron. Nachr. 318, 253

R2	Cuffey J. 1938, Ann. Harv. Coll. Obs. 106,39

R3	Grubissich C. 1973, Astron. Astrophys. Suppl. 11, 287

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