  A special Danielewski surface is an affine surface which is the total space
of a principal $(\mathbb{C},+)$-bundle over an affine line with a multiple
origin. Using a fiber product trick introduced by Danielewski, it is known that
cylinders over two such surfaces are always isomorphic provided that both bases
have the same number of origins. The goal of this note is to give an explicit
method to find isomorphisms between cylinders over special Danielewski
surfaces. The method is based on the construction of appropriate locally
nilpotent derivations.
