Impurities in the Heisenberg magnet and the general recipe of Weyl. Lulek, B. — 1991 Séminaire Lotharingien de Combinatoire [electronic only]
The Mac Lane method of construction and classification of extensions of cyclic groups by their automorphism groups. Kuźma, M.; Lulek, B. — 1992 Séminaire Lotharingien de Combinatoire [electronic only]