File photo taken on Dec. 6, 2014 shows Mexican cartoonist Sixto Valencia Burgos (C) who drew the character "Memin Pinguin" at the International Book Fair in Guadalajara, Mexico. Sixto Valencia Burgos died of a heart attack on Thursday at the age of 81, according to local press. (Xinhua/Javier Lira Otero/NOTIMEX)