Hurd, Paul D. (Paul David),   1921-. <br/><br/>
Principal sunflower bees of North America with emphasis on the southwestern United States(Hymenoptera :  Apoidea) / 
Paul D. Hurd, Wallace E. La Berge and E. Gorton Linsley. 
 - Washington :  Smithsonian Institution Press,  1980. 
 - 157p. :  ill. ;  26 cm. 
 - Smithsonian contributions to zoology  no. 310 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>Bees--United States.<br/>Helianthus.