Lanczos,C, <br/><br/>
Linear Differential Operators 
By Cornelius Lanczos 
 - United States  Dover Publications, INC.  1997 
 - xvi;564p. 
<br/><br/><label>ISBN: </label>0-486-68035-5 
<br/><br/><label>Dewey Class. No.: </label>B33  / N7