H. R. Merrett et al.. A deep kinematic survey of planetary nebulae in the Andromeda galaxy using the Planetary Nebula Spectrograph. „Monthly Notices of the Royal Astronomical Society”. 369 (1), s. 120-142, 2006-06-11. DOI: 10.1111/j.1365-2966.2006.10268.x. (ang.).