Population dynamics in two-patch environments: some anomalous consequences of an optimal habitat distribution. Theoretical Population Biology. October 1985, 28 (2): 181–208. doi:10.1016/0040-5809(85)90027-9.
Sources, sinks, and population regulation. The American Naturalist. November 1988, 132 (5): 652–61. doi:10.1086/284880.