Graph minors. XI: Circuits on a surface
This paper provides preliminary work to be applied towards proving a theorem on graphs with the exclusion of a fixed minor. One component of this proof involves graphs drawn on a surface. The lemmas of the current paper enable the authors to treat the case where the surface is a sphere in the same manner as the case of higher genus. The main tool is the tangle, defined in earlier papers by the authors.
scientific article; zbMATH DE number 562397