Teodorescu, A. M., Méndez, R. H., Bernardi, F., Thomas, J., Das, P., & Gerhard, O. (2011). Planetary nebulae in the elliptical galaxy NGC 4649 (M 60): kinematics and distance redetermination. The Astrophysical Journal, 736(1): 65, pp. 1-16. doi:10.1088/0004-637X/736/1/65.