He is the coauthor with Stephen E. Zepf of Globular Cluster Systems, and was one of three scientists (the others being François Schweizer and Steve Zepf) to suggest the formation of young globular clusters by colliding spirals might explain the large number of globular clusters present in elliptical galaxies. This was later supported by the findings of the Hubble Space Telescope.
This researcher collaborated with Stephen E. Zepf on Globular Cluster Systems, and he was among three scientists (François Schweizer and Steve Zepf being the others) who proposed that the collision of spirals might be responsible for the formation of young globular clusters in elliptical galaxies. This hypothesis was later confirmed by the Hubble Space Telescope's findings.