Tense operators on m-symmetric algebras
  Here we initiate an investigation of the equational classes of m-symmetric algebras endowed with two tense operators. These varieties is a generalization of tense algebras. Our main interest is the duality theory for these classes of algebras. In order to do this, we require Urquart's duality for Ockham algebras and Goldblatt's duality for bounded distributive lattice with operations. The dualities enable us to describe the lattices of congruences on tense m-symmetric algebras. 
Aldo V. Figallo, Carlos Gallardo and Gustavo Pelaitay
math.LO