In the course of a project I am developing I have to use a classical result in topological graph theory due to Wagner in which Wagner gives the precise structure of graphs in which $K_5$ is excluded as a minor.
The result (which follows the lines of his proof when excluding $K_5$ and $K_{3,3}$) is in german in the original paper of Wagner (see reference here). So my question is that if someone knows if there exists a modern version of this result and, if possible, in English.
