Strong compact elements in multiplicative lattices
Structure des demi-groupes dont le treillis des sous-demi-groupes est semi-modulaire
Subalgebra modular, distributive and boolean varieties of semigroups
Subgraph isomorphism in planar graphs and related problems.
Sublattices with saturated chains
S-verklebte Summen von Verbänden.
Symmetric difference in orthomodular lattices
Symmetric difference on orthomodular lattices and -valued states
The investigation of orthocomplemented lattices with a symmetric difference initiated the following question: Which orthomodular lattice can be embedded in an orthomodular lattice that allows for a symmetric difference? In this paper we present a necessary condition for such an embedding to exist. The condition is expressed in terms of -valued states and enables one, as a consequence, to clarify the situation in the important case of the lattice of projections in a Hilbert space.