Aller, Lawrence H.; et al. The Spectrum of the Planetary Nebula NGC 6790. Publications of the Astronomical Society of the Pacific. June 1996, 108: 488. Bibcode:1996PASP..108..488A. doi:10.1086/133754.
Aller, Lawrence H.; et al. The Spectrum of the Planetary Nebula NGC 6790. Publications of the Astronomical Society of the Pacific. June 1996, 108: 488. Bibcode:1996PASP..108..488A. doi:10.1086/133754.