On the relative importance of excluded minors
  If EE is a set of matroids, then ex(EE) denotes the set of matroids that have no minor isomorphic to a member of EE. If EE' is a subset of EE, we say that EE' is /superfluous/ if ex(EE - EE') - ex(EE) contains only finitely many 3-connected matroids. We characterize the superfluous subsets of six well-known collections of excluded minors. 
Rhiannon Hall, Dillon Mayhew, Stefan H. M. van Zwam
math.CO