From the introduction: We consider the following integral boundary value problem for nonlinear fractional differential equation: \[ \begin{gathered} D^q x(t)= f(t,x(t)),\quad t\in J= [0,T],\;T> 0,\\ x(0)=\lambda \int^T_0,\\ x(s)\,ds+ d,\quad d\in\mathbb R,\end{gathered} \] where \(f\in C(J\times\mathbb R,\mathbb R)\), \(\lambda\geq 0\) and \(0<q<1\).
The lower and upper solutions combined with monotone iterative technique is applied. Problems of existence and unique solutions are discussed.