Isoperimetric problems of the calculus of variations with fractional   derivatives
  In this paper we study isoperimetric problems of the calculus of variations with left and right Riemann-Liouville fractional derivatives. Both situations when the lower bound of the variational integrals coincide and do not coincide with the lower bound of the fractional derivatives are considered. 
Ricardo Almeida, Rui A. C. Ferreira, Delfim F. M. Torres
math.OC