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  • Green index in semigroups : generators, presentations and automatic structures 

    Cain, A.J.; Gray, R; Ruskuc, Nik (2012) - Journal article
    The Green index of a subsemigroup T of a semigroup S is given by counting strong orbits in the complement S n T under the natural actions of T on S via right and left multiplication. This partitions the complement S nT ...
  • Subalgebras of FA-presentable algebras 

    Cain, A.J.; Ruskuc, Nik (2014-06) - Journal article
    Automatic presentations, also called FA-presentations, were introduced to extend finite model theory to infinite structures whilst retaining the solubility of fundamental decision problems. This paper studies FA-presentable ...