On the lattice of convex subsets of a partial monounary algebra Danica Jakubíková-Studenovská (1989) Czechoslovak Mathematical Journal
On the partial semi-hypergroups with empty diagonal M. De Salvo (1999) Acta Universitatis Carolinae. Mathematica et Physica
On the tensor product of a Boolean algebra and an orthoalgebra David J. Foulis, Pavel Pták (1995) Czechoslovak Mathematical Journal