Rydberg, Per Axel,  860-1931 <br/><br/>
Flora of the prairies and plains of cental North America / 
by Per Axel Rydberg 
 - New York :  Hafner Publishing Company,  1965 
 - vii, 969 p. :  ill. ;  24 cm. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Botany--North America<br/>Pteridophyta<br/>Phanerogams