Nicko van Someren Andrew M. Odlyzko Ronald L. Rivest Tim Jones Duncan Goldie-Scot Does Anyone Really Need MicroPayments? 69-76 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2742&spage=69 2003 conf/fc/2003 Financial Cryptography db/conf/fc/fc2003.html#SomerenORJG03