2 × 2 monotone grid classes are finitely based
Michael Albert, Robert Brignall · Open Research Online (The Open University) · 2016
In this note, we prove that all 2×2 monotone grid classes are finitely based, i.e., defined by a finite collection of minimal forbidden permutations. This follows from a slightly more general result about certain 2×2 (generalized) grid classes having two monotone cells in the same row.