Pennak, Robert W. <br/><br/>
Fresh-water invertebrates of the United States / 
by Robert W. Pennak 
 - New York :  The Ronald Press Co.,  1953 
 - ix, 769 p. :  ill. ;  25 cm. 
<br/><br/>Includes bibliography 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Freshwater invertebrates--United States