Nuttiyettu upanishathukal / 
edited by P. N. Unni 
 - 5th ed. 
 - Thiruvananthapuram :  Prasanthi Publishers,  2006. 
<br/><br/><br/>In Malayalam 
<br/><br/><label>ISBN: </label>8190237667 
<br/><br/><label>Subjects--Index Terms: </label>Philosophy - Indian Upanishad