Protter, M.H & Wein-Berger, H.F <br/><br/>
Maximum principles in differential equations 
M.H. Protter & H.F. Wein-Berger 
 - New York  Springer  1967 
 - x  261 
 - Prentice-hall partial differential equations series .
<br/><br/><label>ISBN: </label>3540960686 
<br/><br/><label>Dewey Class. No.: </label>10.02  / PROT