Fedoryuk, Mikhail V. <br/><br/>
Asymptotic analysis  linear ordinary differential equations 
by Mikhail V Fedoryuk 
 - Berlin  Springer-Verlag  1993 
 - viii, 363p. 
<br/><br/><label>ISBN: </label>3540548106 
<br/><br/><label>Dewey Class. No.: </label>515.352  / N936