Penny-Packing and Two-Dimensional Codes.
Perfect codes in Cartesian products of 2-paths and infinite paths.
Perfect codes in graphs and their Cartesian powers [Abstract of thesis]
Picture codes
We introduce doubly-ranked (DR) monoids in order to study picture codes. We show that a DR-monoid is free iff it is pictorially stable. This allows us to associate with a set C of pictures a picture code B(C) which is the basis of the least DR-monoid including C. A weak version of the defect theorem for pictures is established. A characterization of picture codes through picture series is also given.