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Pandey, A. K.; Upadhyay, K.; Ogura, K.; Sagar, Ram; Mohan, V.; Mito, H.; Bhatt, H. C.; Bhatt, B. C. (2005). “Stellar contents of two young open clusters: NGC 663 and 654”. Monthly Notices of the Royal Astronomical Society358 (4): 1290-1308. Bibcode: 2005MNRAS.358.1290P. doi:10.1111/j.1365-2966.2005.08784.x.
Negueruela, I.; Gonzalez-Fernandez, C.; Marco, A.; Clark, J. S. (2011). “A massive association around the obscured open cluster RSGC3”. Astronomy & Astrophysics528. Bibcode: 2011A&A...528A..59N. doi:10.1051/0004-6361/201016102.
Humphreys, R. M. (1978). “Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.”. Astrophysical Journal Supplement Series38: 309-350. Bibcode: 1978ApJS...38..309H. doi:10.1086/190559.