Ehlers, V. M. (1958). Municipal And Rural Sanitation Victor M. Ehlers And Ernest W. Steel. McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Ehlers, Victor M. Municipal And Rural Sanitation Victor M. Ehlers And Ernest W. Steel. McGraw-Hill, 1958.
Lua MLA (8ú heag.)Ehlers, Victor M. Municipal And Rural Sanitation Victor M. Ehlers And Ernest W. Steel. McGraw-Hill, 1958.
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