Lanczos, Cornelius. <br/><br/>
The variational principles of mechanics   

 - 4th 
 - New York  Dover  1986 
 - xxix, 418p. Index, Bibl. 
<br/><br/> "Unabridged republication of the 4th ed. published by Univ. of Toronto Pr., Toronto, 1970".   
<br/><br/><label>Dewey Class. No.: </label>530.1  / L252.VP