Integrated spectrum of the planetary nebula NGC 7027

Y. Zhang, X.-W. Liu, S.-G. Luo, D. Péquignot, M. J. Barlow
2007 Astronomy and Astrophysics  
doi:10.1051/0004-6361:20052869e fatcat:yg7f3uwikvf7jktxarj2kgn6nm