Benchohra, M.Karapınar, E.Lazreg, J.E.Salim, A.2025-08-052025-08-0520231938-1743https://doi.org/10.1007/978-3-031-26928-8_2https://hdl.handle.net/20.500.12416/10307In this chapter, we discuss the necessary mathematical tools, notations, and concepts we need in the succeeding chapters. We look at some essential properties of fractional differential operators. We also review some of the basic properties of measures of noncompactness and fixed point theorems which are crucial in our results regarding fractional differential equations. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.eninfo:eu-repo/semantics/closedAccessBook Part10.1007/978-3-031-26928-8_22-s2.0-85159426914