एपीए उद्धरण

Helly,Walter. (1975). Urban systems models. Academic Press, INC.

शिकागो स्टाइल उद्धरण

Helly,Walter. Urban Systems Models. New York: Academic Press, INC, 1975.

एमएलए उद्धरण

Helly,Walter. Urban Systems Models. Academic Press, INC, 1975.