John, Fritz. <br/><br/>
Partial Differential Equations /  

 - Third Ed. /  
 - New Delhi-2 :   Narosa Publishing House ,   1981 
 - p.194 :  
<br/><br/><label>ISBN: </label>3-540-78022-X 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Mathematics
<br/><br/><label>Dewey Class. No.: </label>B334  / L1,L8;3