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Dachs, J.; Eichendorf, W.; Schleicher, H.; Schmidt-Kaler, T.; Stift, M.; Tug, H. Photoelectric scanner measurements of Balmer emission line profiles for southern Be stars. II. A survey for variations. Astronomy & Astrophysics. March 1981, 43: 427–453. Bibcode:1969ApJ...157..313H. doi:10.1086/190820.