The purpose of this note is two-fold. Firstly, we prove that the variety RDMSH1 of regular De Morgan semi-Heyting algebras of level 1 satisfies Stone identity and present (equational) axiomatizations for several subvarieties of RDMSH1. Secondly, using our earlier results published in 2014, we give a concrete description of the lattice of subvarieties of the variety RDQDStSH1 of regular dually quasi-De Morgan Stone semi-Heyting algebras that contains RDMSH1. Furthermore, we prove that every subvariety of RDQDStSH1, and hence of RDMSH1, has Amalgamation Property. The note concludes with some open problems for further investigation.
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An earlier paper characterized all subdirectly irreducible permutational fibered automata. This paper characterizes all subdirectly irreducible fibered automata which are not permutational. The characterization is both graphtheoretical and algebraic.
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A permutational automaton is a fibered automaton with one-element event set or an empty state space. This paper characterizes all subdirectly irreducible permutational automata.
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