Ehlers, V. M., & Steel, E. W. 1. (1958). Municipal and rural sanitation (5th ed.). McGraw-Hill.
Cita Chicago (17th ed.)Ehlers, Victor Marcus, i Ernest William 1893 Steel. Municipal and Rural Sanitation. 5th ed. New York: McGraw-Hill, 1958.
Cita MLA (9th ed.)Ehlers, Victor Marcus, i Ernest William 1893 Steel. Municipal and Rural Sanitation. 5th ed. McGraw-Hill, 1958.
Atenció: Aquestes cites poden no estar 100% correctes.