Tense SHn--algebras
  In 1982, L. Iturrioz introduced symmetrical Heyting algebras of order n (or SHn-algebras). In this paper, we define and study tense SHn-algebras namely, SHn-algebras endowed with two tense operators. These algebras constitute a generalization of tense Lukasiewicz-Moisil algebras. Our main interest is the duality theory for tense SHn- algebras. In order to do this, we requiere Esakia's duality for Heyting algebras and Goldblatt's duality for bounded distributive lattices with operations. 
Aldo V. Figallo and Gustavo Pelaitay
math.LO