Answer:
Reuter, P. and MacCoun R. "Weighing the Harms of Cannabis Use and Production." Proceedings International Psychosis Conference. Melbourne: Department of Human Studies, 1999.
Commentary:
Firstly, include an "and" between the names of both authors.
Secondly, The addition of "Australia" after Melbourne is probably not necessary. A comma should separate the publisher "Department of Human Studies" and the year of publication.