State of Illinois Division of the State Water Survey(1928-29 <br/><br/>
Studies on two-stage sludge digestion   
by Department of Registration & Education, State of Illinois 
 - Illinois  State of Illinois  1930 
 - 92p 
 - Illinois State Water Survey No.29 .
<br/><br/><label>Dewey Class. No.: </label>628.1  / N30