1. Abdellaoui M.A., Dahmani Z., Solvability for a Coupled System of Nonlinear Fractional Integro-Differential Equations, Note Di Matematica, Vol. 35, No. 1 (2015), 95–107.

2. Agrawal O.P., Generalized Euler–Lagrange Equations and Transversality Conditions for FVPs in Terms of the Caputo Derivative, J. Vib. Control., Vol. 13, No. (9-10) (2007), 1217–1237.

3. Agrawal O.P., Generalized Variational Problems and Euler–Lagrange Equations, Comput. Math. Appl., Vol. 59, No. 5 (2010), 1852–1864.

4. Almeida R., Fractional Variational Problems with the Riesz–Caputo Derivative, Appl. Math. Lett., Vol. 25 (2012), 142–148.

5. Almeida R., Ferreira R.A.C., Torres D.F.M., Isoperimetric Problems of the Calculus of Variations with Fractional Derivatives, Acta Mathematica Scientia, Vol. 32 (2012), 619–630.

6. Almeida R., Malinowska A.B., Torres D.F.M., Fractional Euler–Lagrange Differential Equations Via Caputo Derivatives, Fractional Dynamics and Control, Springer New York, (2012), 109–118.

7. Almeida R., Torres D.F.M., Calculus of Variations with Fractional Derivatives and Fractional Integrals, Appl. Math. Lett., Vol. 22, No. 12 (2009), 1816–1820.

8. Almeida R., Torres D.F.M., Necessary and Sufficient Conditions for the Fractional Calculus of Variations with Caputo Derivatives, Commun. Nonlinear Sci.Numer. Simul., Vol. 16 (2011), 1490–1500.

9. Almeida R., Tavares D., Torres D.F.M., The variable-order fractional calculus of variations, Springer, 2019.

10. Anber A., Dahmani Z., The Variational Iteration Method For Solving the Fractional Coupled Lotka–Volterra Equation, JIM., Vol. 14, No. 4 (2011), 373–388.

11. Atanackovi´c T.M., Konjik S., Pilipovi´c S., Variational Problems with Fractional Derivatives: Euler–Lagrange equations, J. Phys. A., Vol. 41, No. 9 (2008), 1–12.

12. Bourdin L., Odzijewicz T., Torres D.F.M., Existence of Minimizers for Fractional Variational Problems Containing Caputo Derivatives, Adv. Dyn. Syst. Appl., Vol. 8 (2013), 3–12.

13. Brunt B.V., The Calculus of Variations, Universitext, Springer, New York, 2004.

14. Carath´eodory C., Calculus of Variations and Partial Differential Equations of the First Order, Chelsea, 1982.

15. Dahmani Z., Ta¨ıeb A., A Coupled System of Fractional Differential Equations Involving Two Fractional Orders, ROMAI Journal, Vol. 11, No. 2 (2015), 141–177.

16. Dahmani Z., Ta¨ıeb A., New Existence and Uniqueness Results for High Dimensional Fractional Differential Systems, Facta Nis Ser. Math. Inform., Vol. 30, No. 3 (2015), 281–293.

17. Gelfand I.M., Fomin S.V., Calculus of Variations, Moscow State University, Revised English EditionTranslated and Edited by R.A. Silverman, Prentice-Hall, INC., 1963.

18. Hilfer R., Applications of Fractional Calculus in Physics, World Scientific, River Edge, New Jersey, 2000.

19. Kilbas A.A., Srivastava H.M., Trujillo J.J., Theory and Applications of Fractional Differential Equations, Elsevier B.V., Amsterdam, The Netherlands, 2006.

20. Klafter J., Lim S.C., Metzler R., Fractional Dynamics, Recent Advances, World Scientific, Singapore, 2011.

21. Klimek M., On Solutions of Linear Fractional Differential Equations of a Variational Type, The Publishing Office of the Czestochowa University of Technology, Czestochowa, 2009.

22. Malinowska A.B., Odzijewicz T., Torres D.F.M., Advanced Methods in the Fractional Calculus of Variations, Cham: Springer, 2015.

23. Malinowska A.B., Torres D.F.M., Generalized Natural Boundary Conditions for Fractional Variational Problems in Terms of the Caputo Derivative, Comput. Math. Appl., Vol. 59, No. 9 (2010), 3110–3116.

24. Malinowska A.B., Torres D.F.M., Introduction to the Fractional Calculus of Variations, Imperial College Press, 2012.

25. Miller K.S., Ross B., An Introduction to the Fractional Calculus and Fractional Differential Equations, Wiley, New York, 1993.

26. Oldham K.B., Spanier J., The Fractional Calculus, Academic Press, New York, 1974.

27. Riewe F., Nonconservative Lagrangian and Hamiltonian Mechanics, Phys. Rev. E 3, Vol. 53, No. 2 (1996), 1890–1899.

28. Samko S.G., Kilbas A.A., Marichev O.I., Fractional Integrals and Derivatives Theory and Applications, Gordon and Breach: Amsterdam, 1993.

29. Taïeb A., Dahmani Z., A coupled system of nonlinear differential equations involving m nonlinear terms, Georgian Math. Journal, Vol. 23, No. 3 (2016), 447–458.

30. Taïeb A., Dahmani Z., The high order Lane-Emden fractional differential system: Existence, uniqueness and Ulam stabilities, Kragujevac Journal of Mathematics, Vol. 40, No. 2 (2016), 238–259.

31. Taïeb A., Dahmani Z., Some Fractional Variational Problerms Involving Caputo Derivatives, (Submitted).

32. Taïeb A., Existence of Solutions and the Ulam Stability for a Class of Singular Nonlinear Fractional Integro-Differential Equations, Communications in Optimization Theory, Vol. 2019 (2019), Article ID 4, 1–22.

33. Taïeb A., Stability of Singular Fractional Systems of Nonlinear Integro-Differential Equations, Lobachevskii Journal of Mathematics, Vol. 40, Issue 2 (2019), 219–229.

34. Weinstock R., Calculus of Variations with Applications to Physics and Engineering, Dover, 1974.

35. Yourgrau W., Mandelstam S., Variational Principles in Dynamics and Quantum Theory, W. B. Saunders Company, Philadelphia, 1968.

36. Yousefi S.A., Dehghanb M., Lotfi A., Generalized Euler–Lagrange Equations for Fractional Variational Problems with Free Boundary Conditions, Computers and Mathematics with Applications, Vol. 62 (2011), 987–995.