David A. Cornell.Principia Astronomical Observatory (англ.) // International Amateur-Professional Photoelectric Photometry Communication. — 1999. — June (no. 76). — P. 62-67. — ISSN0886-6961.
David A. Cornell.Principia Astronomical Observatory (англ.) // International Amateur-Professional Photoelectric Photometry Communication. — 1999. — June (no. 76). — P. 62-67. — ISSN0886-6961.