GREENWOOD, N., & EDWARDS, J. (1979). Human environments and natural systems. -- 2nd ed. Duxbury Press.

GREENWOOD, N.H, and J.M.B EDWARDS. Human Environments and Natural Systems. -- 2nd Ed. North Scituate: Duxbury Press, 1979.

GREENWOOD, N.H, and J.M.B EDWARDS. Human Environments and Natural Systems. -- 2nd Ed. Duxbury Press, 1979.