1. Pöschel, R.,Concrete representation of algebraic structures and general Galois Theory, in: Contributions to General Algebra, Proc. Klagenfurt Gonf. 1978, 249–272.
2. Schein, B. M.,Involuted restrictive bisemigroups of binary relations, Mat. Fyz. Çasopis SAV19 (1969), 307–315.