Keenan, Philip C; McNeil, Raymond C (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
Keenan, Philip C; McNeil, Raymond C (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
Antal, M. (1962), "Observations of occultations at the Observatory Skalnaté Pleso in the year 1961", Bulletin of the Astronomical Institute of Czechoslovakia, 13: 164, Bibcode:1962BAICz..13..164A.