Unverified accounts that first appeared in books published more than 140 years after Banneker's death relate that, as a young teenager, Banneker met and befriended Peter Heinrich, a Quaker who later established a school near the Banneker family farm.(2) Bedini, 1972, p. 300. "Martha Tyson's posthumous book was the last work about Banneker to be based on original materials. During the next several decades, numerous articles in periodicals and newspapers mentioned Banneker's life and works, but each was based on earlier publications without contributing new materials. ... Finally, in 1949 another biography of Banneker appeared. This work by Shirley Graham was highly fictionalized and written for young people. It became popular, but the lack of distinction between fact and fiction in its presentation, while a compliment to the writing skill of Shirley Graham, has resulted in yet more confusion concerning Banneker's achievements and their importance."</ref>(2) Corrigan, 2003, p. 2 "Cerami constructs a credible narrative of Banneker's life, but fails to document his research."</ref> (Quakers were leaders in the anti-slavery movement and advocates of racial equality (see Quakers in the abolition movement and Testimony of equality)). These accounts state that Heinrich shared his personal library and provided Banneker with his only classroom instruction. Banneker's formal education (if any) presumably ended when he was old enough to help on his family's farm.