“…For some recent results on the existence, nonexistence and multiplicity of positive solutions for fractional differential equations and systems of fractional differential equations with various boundary conditions, we refer the reader to the monographs [10,36] and the papers [2,3,8,12,13,17,19,25,28,30,31,34]. We also mention the books [14,15,24,26,27] and the papers [5-7, 21-23, 29] for applications of the fractional differential equations in various disciplines.…”