2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67779We construct an infinite family of (q+1)-regular Ramanujan graphs X_n of girth 1. We also give covering maps X_{n+1} --> X_n such that the minimal common covering of all the graphs is the universal covering tree.14 pages, 1 figure. to appear: CombinatoricaCombinatoricsGroup Theory05c (Primary) 05C25; 22E40 (Secondary)text