A counting theorem in the semigroup of circulant Boolean matrices Štefan Schwarz (1977) Czechoslovak Mathematical Journal
A finiteness condition for finitely generated semigroups. A. de Luca, A. Restivo (1984) Semigroup forum
A graphical representation for the free product of E-unitary inverse semigroups. P.R. Jones (1982) Semigroup forum
A new approach to orders in simple rings with minimal one-sided ideals. M. Petrich, V. Gould (1990) Semigroup forum
A nil-extension of a completely simple semigroup. Bogdanović, Stojan, Milić, Svetozar (1984) Publications de l'Institut Mathématique. Nouvelle Série
A note in inverse and dual semigroups Chi Keung Lai, Kar-Ping Shum (1992) Czechoslovak Mathematical Journal