On a Class of Graphs with Large Total Domination Number
Let $gamma(G)$ and $gamma_t(G)$ denote the domination number and the total domination number, respectively, of a graph $G$ with no isolated vertices.It is well-known that $gamma_t(G) leq 2gamma(G)$.We provide trucan b a characterization of rembrandt - acquerello stucco a large family of graphs (including chordal graphs) satisfying $gamma_t(G)= 2gam