Paristhithi sastreeya veekshanam / 
edited by N. V. P. Unithiri 
 - 2nd ed. 
 - Thiruvananthapuram :  State Institute of Languages,  2012. 
<br/><br/><br/>In Malayalam 
<br/><br/><label>ISBN: </label>9788176381611 
<br/><br/><label>Subjects--Index Terms: </label>Environmental Biology