2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/75470Let $X$ be an affine surface admitting a unique affine ruling and a $\mathbb C^*$-action. Assume that the ruling has a unique degenerate fibre and that this fibre is irreducible. In this paper we give a short proof of the following result of Miyanishi and Masuda: the universal covering of $X$ is a hypersurface in the affine 3-space given by the equation $x^my=z^d-1$, where $m>1$.3 pagesAlgebraic Geometry14R05; 14R20; 14R25text