On generalizing Stallings' pregroup
The aim of this paper is to prove that for a pregroup \(P\) the axioms \(P_ 1\) to \(P_ 4\) together with the axiom \([Q_ 5]\) are sufficient to prove a normal form theorem (we recall the axiom \([Q_ 5]\): If \(ab\), \(bc\), \(cd\), and \(de\) are defined then at least one of \(abc\), \(bcd\), and \(cde\) is defined).
scientific article; zbMATH DE number 33038