Popper, Daniel M. A Peculiar B-Type Spectrum. Publications of the Astronomical Society of the Pacific. June 1942, 54 (319): 160–161. Bibcode:1942PASP...54..160P. doi:10.1086/125431.
Jeffery, C. S.; Heber, U.; Hill, P. W.; Dreizler, S.; Drilling, J. S.; Lawson, W. A.; Leuenhagen, U.; Werner, K. A catalogue of hydrogen-deficient stars. Jeffery, C. S.; Heber, U. (编). Hydrogen deficient stars, Proceedings 96. Bamberg, Germany: Astronomical Society of the Pacific Conference Series. August 28 – September 1, 1995 (1996). Bibcode:1996ASPC...96..471J.请检查|publication-date=中的日期值 (帮助)
Popper, Daniel M. A Peculiar B-Type Spectrum. Publications of the Astronomical Society of the Pacific. June 1942, 54 (319): 160–161. Bibcode:1942PASP...54..160P. doi:10.1086/125431.