2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/74294In 1963 Fisher and Stephenson \cite{FS} conjectured that the monomer-monomer correlation on the square lattice is rotationally invariant. In this paper we prove a closely related statement on the hexagonal lattice. Namely, we consider correlations of two quadromers (four-vertex subgraphs consisting of a monomer and its three neighbors) and show that they are rotationally invariant.28 pagesCombinatoricsClassical Analysis and ODEs05text