Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Leggett, S. K.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Monet, David G.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy; Vrba, Frederick J.; Walker, Richard L. (2007). Trigonometric Parallaxes of Central Stars of Planetary Nebulae. Astronomical Journal. 133 (2): 631—638. Bibcode:2007AJ....133..631H. doi:10.1086/510348.
Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Leggett, S. K.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Monet, David G.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy; Vrba, Frederick J.; Walker, Richard L. (2007). Trigonometric Parallaxes of Central Stars of Planetary Nebulae. Astronomical Journal. 133 (2): 631—638. Bibcode:2007AJ....133..631H. doi:10.1086/510348.