Coddington, E.A & De Snoo, H.S.V <br/><br/>
Regular boundary value problems associated with pairs of ordinary differential expressions 
E.A. Coddington & H.S.V. De Snoo 
 - Berlin  Springer  1981 
 - 225 
 - Lecture notes in mathematics 858 .
<br/><br/><label>ISBN: </label>35401070611 
<br/><br/><label>Dewey Class. No.: </label>10.01+22  / CODD