Shulka, A.C.. <br/><br/>
Essentials of Paleobotany /  

 - Second Rev. Ed. /  
 - New Delhi-2 :   Vikas Publishing House Pvt. Ltd.. 
 - p.377 :  
<br/><br/><label>ISBN: </label>0-7069-1451-1 
<br/><br/><label>Dewey Class. No.: </label>I:8  / L5S, M2;1