Ching-Nung Yang Hsu-Tun Teng An Efficient Method for Finding Minmum Hash Chain of Multi-Payword Chains in Micropayment. 45-48 2003 conf/wecwis/2003 CEC http://csdl.computer.org/comp/proceedings/cec/2003/1969/00/19690045abs.htm db/conf/wecwis/cec2003.html#YangT03