References for the numbering systems

Col	Reference

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

R1	Marx S., Lehmann H. 1979, Astron. Nach. 300, 295 

R2	Subramaniam A., Bhatt B.C. 2007, Mon. Not. R. Astron. Soc. 377, 829

R3	Maciejewski G. & Niedzielski A. 2007, Astron. Astrophys. 467, 1065

R4	Glushkova E.V., et al. 2010, Astron. Lett. 36, 14 

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