Irreducibility of L(2, 1)-coloring and Inh-Colorability of Some Classes of Graphs. - Renu C. Laskar; John Villalpando (Electron. Notes Discret. Math., 2003)

Acyclic colorings of products of trees. - Robert E. Jamison; Gretchen L. Matthews; John Villalpando (Inf. Process. Lett., 2006)

On irreducible no-hole L(2, 1)-coloring of trees. - Renu C. Laskar; Gretchen L. Matthews; Beth Novick; John Villalpando (Networks, 2009)