Peg Mullen, 92, an author and former Iowa farm wife who hounded the U.S. military to find the truth about her son's death in Vietnam, died Friday in La Porte City, Iowa.

Peg Mullen wrote the 1995 book "Unfriendly Fire: A Mother's Memoir" after her son Michael died at age 25 when a U.S. artillery shell fell short and killed him on Feb. 18, 1970, near the South Vietnamese village of Tu Chanh.

"This is the first book you've got from the family side of a Vietnam story," Mullen told the Associated Press at the time. "All you've read everywhere is the blood and the guts. But you haven't had anything coming out of what went on as far as the family, as far as brothers and sisters and mothers and dads."

Her other son, John Mullen, said Sunday that he doesn't know if his mother was ever satisfied with the information she tracked down, "but she came to terms with it."

Mercedes Sosa, 74, an Argentine singer who emerged as a electrifying voice of conscience throughout Latin America for songs that championed social justice, died Sunday in Buenos Aires. With a rich contralto voice, the Latin Grammy winner performed with entertainers as varied as rock star Sting and folk singer Joan Baez.