The Abacus: A History http://fenris.net/~lizyoung/abacus.html The Abacus: A History http://fenris.net/~lizyoung/abacus.html The Abacus: A History, Young, L. 2004 http://fenris.net/~lizyoung/abacus.html "The Abacus: A History" http://fenris.net/~lizyoung/abacus.html