Graded Posets Inverse Zeta Matrix Formula IIB : The Formula of Inverse ζ-Matrix for Graded Posets with the Finite Set of Minimal Elements via Natural Join of Matrices and Digraphs Technique - B. Weighted Reflexive Reachability Relation

Bulletin de la Société des Science et des Lettres de Łódź. Serie: Recherches sur les Déformations, Tom 61, Numer 1 (2011) s. 129-141
Andrzej Krzysztof Kwaśniewski