A uniqueness method to a new Hadamard fractional differential system with four-point boundary conditions

In this article, we discuss a new Hadamard fractional differential system with four-point boundary conditions [Formula: see text] where [Formula: see text] are two parameters with [Formula: see text] , [Formula: see text] are two real numbers and [Formula: see text] , [Formula: see text] , [Formula: see text] are constants, and [Formula: see text] are the Hadamard fractional derivatives of fractional order. Based upon a fixed point theorem of increasing φ-[Formula: see text] -concave operators, we establish the existence and uniqueness of solutions for the problem dependent on two constants [Formula: see text] .