Joyce Carol Thomas, a prize-winning children's author and champion of multiculturalism, has died. She was 78.

Thomas died Aug. 13 at Stanford University Medical Center in California of cirrhosis of the liver stemming from a bad blood transfusion decades ago, according to her sister, Flora Krasnovsky.

Thomas was best known for her debut book, "Marked by Fire," an autobiographical novel set in her native Oklahoma that won the 1983 National Book Award and the American Book Award, which highlights diversity in literature. Other works included "Bright Shadow," ''Broomwheat Tea" and "The Blacker the Berry."

Thomas was also a three-time nominee for the Coretta Scott King award for outstanding children's books by an African-American.

The author was a board member of the American Book Award's sponsor, the Before Columbus Foundation.