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Demonstratio Mathematica > 2016 > Vol. 49, nr 3 > 252--256

*A*, Ω, + ), where + is a join-semilattice operation and (

*A*, Ω) is an algebra from some given variety . We characterize the free semilattice ordered algebras using the concept of extended power algebras. Next we apply the result to describe the lattice of subvarieties of the variety of semilattice...

Semigroup Forum > 2012 > 85 > 3 > 477-512

*x*

_{1}⋯

*x*

_{ n }≈

*x*

_{1π }

*x*

_{2π }⋯

*x*

_{ nπ }where

*π*is a non-trivial permutation on the set {1,…,

*n*} is called a

*permutation*identity. If

*u*≈

*v*is a permutation identity, then

*ℓ*(

*u*≈

*v*) [respectively

*r*(

*u*≈

*v*)] is the maximal length of the common prefix [suffix] of the words

*u*and

*v*. A variety that satisfies a permutation identity is called

*permutative*. If is a permutative variety,...

Studia Logica > 2012 > 100 > 1-2 > 319-338

**BK**-lattices, show that this class coincides with the abstract closure of the class of twist-structures, and it forms a variety. We prove that the lattice of subvarieties of the variety of

**BK**-lattices is dually isomorphic to the lattice of extensions...

Journal of Algebra > 2011 > 334 > 1 > 1-30

Reports on Mathematical Logic > 2011 > 46 > 3-15

Semigroup Forum > 2010 > 80 > 2 > 341-345

_{ n }be the variety of all epigroups of index ≤

*n*. We prove that, for an arbitrary natural number

*n*, the interval [ℰ

_{ n },ℰ

_{ n+1}] of the lattice of epigroup varieties contains a chain isomorphic to the chain of real numbers with the usual order and an anti-chain of the cardinality continuum.

Algebra universalis > 2008 > 59 > 3-4 > 405-428

*x*

^{2}

*y*=

*xy*

^{2}.

Acta Applicandae Mathematicae > 2005 > 85 > 1-3 > 313-318

Discussiones Mathematicae - General Algebra and Applications > 2004 > 24 > 2 > 267-275

Discussiones Mathematicae - General Algebra and Applications > 2001 > 21 > 2 > 255-268

Reports on Mathematical Logic > 2000 > No. 34 > 79-106