MEXICO CITY — Mexico's president-elect Andres Manuel Lopez Obrador promised Wednesday to investigate the disappearance four years ago of the 43 rural teachers college students, telling parents that his government won't fear the truth.Lopez Obrador stood hand-in-hand with families of the Ayotzinapa students in an emotional gathering marking the day the students went missing while on their way to Iguala, Mexico to protest and raise money.“We shall not fear the truth. Our institutions are strengthened with the truth. It is not true that they will be weakened by an . . .