On finite lattices which are embeddable in subsemigroup lattices. V.B. Repnitskiï (1993) Semigroup forum
On the number of monotonic functions from two-valued logic to k -valued logic Juraj Hromkovič (1985) Kybernetika
On the Word Problem for the Modular Lattice with Four Free Generators. Christian Herrmann (1983) Mathematische Annalen