Rashkov, P., & Rashkova, T.
(1997).
Recursive Constructions in the Theory of P.1. Algebras. // <I>[Third]<D> 3rd International Conference "Development in Language Theory", Thessaloniki, 20 - 23 July 1997: Proc.- Thessaloniki : University of Thessaloniki, 1997, p. 559 - 566..