Lattices of subclasses. II
М. V. Schwidefsky, Anna Zamojska-Dzienio · International Journal of Algebra and Computation · 2014
We prove that the class K(σ) of all algebraic structures of signature σ is Q-universal if and only if there is a class K ⊆ K(σ) such that the problem whether a finite lattice embeds into the lattice of K-quasivarieties is undecidable.