Résumé
We show that, up to renaming of the letters, the only infinite ternary words avoiding the formula ABCAB.ABCBA.ACB.BAC (resp. ABCA.BCAB.BCB.CBA) have the same set of recurrent factors as the fixed point of $0->012,1->02,2->1$Also, we show that the formula ABAC.BACA.ABCA is 2-avoidable. Finally, we show that the pattern ABACADABCA is unavoidable for the class of $C_4$-minor-free graphs with maximum degree 3. This disproves a conjecture of Grytczuk.