Arnaboldi, M., Doherty, M., Gerhard, O., Ciardullo, R., Aguerri, J. A. L., Feldmeier, J. J., et al. (2008). Expansion velocities and core masses of bright planetary nebulae in the Virgo Cluster. The Astrophysical Journal, 674(1), L17-L20. doi:10.1086/528846.