)==Further reading====External links==*Entry in the Encyclopedia of Astrobiology, Astronomy, and Spaceflight*Press release on recent observations of the Cat's Eye Nebula* Planetary Nebulae, SEDS Messier Pages* The first detection of magnetic fields in the central stars of four planetary nebulae* Planetary Nebulae—Information and amateur observations* Planetary nebula on arxiv.org
Энциклопедия «Кругосвет»* Astrolab.ru: Галерея снимков туманностей* Планетарная туманность на сайте Астронет (малая энциклопедия «Физика космоса»)* Planetary Nebulae, SEDS Messier Pages* The first detection of magnetic fields in the central stars of four planetary nebulae* Planetary Nebulae — Information and amateur observations