The Lattice of Subvarieties of {\sqrt{\prime}} quasi-MV Algebras

In the present paper we continue the investigation of the lattice of subvarieties of the variety of ${\sqrt{\prime}}$ quasi-MV algebras, already started in 6]. Beside some general results on the structure of such a lattice, the main contribution of this work is the solution of a long-standing open problem concerning these algebras: namely, we show that the variety generated by the standard disk algebra D _r is not finitely based, and we provide an infinite equational basis for the same variety.