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math.RA2020
Reflections and powers of multisorted minions
Erkko Lehtonen, Reinhard Pöschel
Classes of multisorted minions closed under extensions, reflections, and direct powers are considered from a relational point of view. As a generalization of a result of Barto, Opr…
math.RA2019
Graph quasivarieties
Erkko Lehtonen, Reinhard Pöschel
Introduced by C. R. Shallon in 1979, graph algebras establish a useful connection between graph theory and universal algebra. This makes it possible to investigate graph varieties…