Pakull, M. W. (1991). «Spectrophotometry of Ring Nebulae around Wolf-Rayet Stars». Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies: Proceedings of the 143rd Symposium of the International Astronomical Union held in Sanur, Bali, Indonesia, June 18-22, 1990.: 391. Bibcode:1991IAUS..143..391P. Consultado el 20 de marzo de 2023.
Pakull, M. W. (1991). «Spectrophotometry of Ring Nebulae around Wolf-Rayet Stars». Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies: Proceedings of the 143rd Symposium of the International Astronomical Union held in Sanur, Bali, Indonesia, June 18-22, 1990.: 391. Bibcode:1991IAUS..143..391P. Consultado el 20 de marzo de 2023.