Severin, Henry H.P. <br/><br/>
Symptoms induced by some species of aphids feeding on ferns. 

 -  1950. 
 - s. 81-91, [1] :  il. ;  24 cm. 
 - Hilgardia  Vol. 20 No. 5 .
<br/><br/>bibliogr. 
 = Hilgardia.