Stephani, Hans. <br/><br/>
Differential Equations :their solution using symmetries 
Hans Stephani, Malcolm MacCallum, 
 - New york :  Cambridge University Press,  1989. 
 - 260 p. ;  21 cm. 
 - Cambridge monographs on mathematical physics. .
 - Cambridge monographs on mathematical physics. .
<br/><br/><label>ISBN: </label>0521355311 0521366895 
<br/><br/><label>Dewey Class. No.: </label>515.35