1. Commutative semigroups that are nil of index 2 and have no irreducible elements Creator: Ježek, Jaroslav, Kepka, Tomáš, and Němec, Petr Format: bez média and svazek Type: model:article and TEXT Subject: nil-semigroup and commutative nil-semigroup Language: English Description: Every commutative nil-semigroup of index 2 can be imbedded into such a semigroup without irreducible elements. Rights: http://creativecommons.org/publicdomain/mark/1.0/ and policy:public