1. A. M. Nakhushev, Fractional Calculus and Its Application (Fizmatlit, Moscow, 2003) [in Russian].
2. A. A. Kilbas, H. M. Srivastava, and J. J. Trujillo, Theory and Applications of Fractional Differential Equations, Vol. 204 of North Holland Math. Studies (Elsevier Science, Amsterdam, 2006).
3. A. V. Pskhu, ‘‘Initial-value problem for a linear ordinary differential equation of noninteger order,’’ Sb. Math. 202, 571–582 (2011).
4. A. M. Najafov, ‘‘On some properties of fractional order Sobolev spaces,’’ Trans. Natl. Azerb., Ser. Phys.-Tech. Mat. Sci., Iss. Mat. Mech. 30 (7), 123–133 (2010).
5. A. M. Najafov, ‘‘Trace theorems in fractional Sobolev space and their applications,’’ Casp. J. Appl. Math., Ecol. Econ. 1 (2), 87–94 (2013).