  Fractional (or non-integer) differentiation is an important concept both from
theoretical and applicational points of view. The study of problems of the
calculus of variations with fractional derivatives is a rather recent subject,
the main result being the fractional necessary optimality condition of
Euler-Lagrange obtained in 2002. Here we use the notion of Euler-Lagrange
fractional extremal to prove a Noether-type theorem. For that we propose a
generalization of the classical concept of conservation law, introducing an
appropriate fractional operator.
