$2\times 2$ monotone grid classes are finitely based
Authors: Albert, Michael and Brignall, Robert
In this note, we prove that all $2 \times 2$ 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 $2
\times 2$ (generalized) grid classes having two monotone cells in the same row.