Calculus of variations 
Gelʹfand, I. M. 
 - Rev. English ed. 
 - Englewood Cliffs, N.J.,  Prentice-Hall  1963 
 - vii, 232 p.  diagrs.  24 cm. 
 - Selected Russian publications in the mathematical sciences .
<br/><br/><label>ISBN: </label>NULL