Numerical method with guaranteed accuracy of a double turning point for a radially symmetric solution of the perturbed Gelfand equation

We describe a numerical method with guaranteed accuracy to enclose a double turning point for a radially symmetric solution of the perturbed Gelfand equation. We use Nakaoʹs method and a system of equations defined on an extended space to enclose a double turning point. We describe verification procedures in detail and give a numerical example.