On a classification problem for a quiver of type $\widetilde{A}_{3}$

We present a new solution to the classification problem for the category of representations of a quiver of type $\widetilde{A}_{3}$. Our approach uses linear algebra techniques which lead us to a reduction that allows to use induction. As an application, the solution to the classical Kronecker problem and its contragredient version are obtained in an elementary way. We also describe the endomorphism rings for the indecomposable representations and an algorithm that shows how to reconstruct their matrix form from some graphic invariants.