4G.P.Dwyer. The economics of Bitcoin and similar private digital currencies [J]. Journal of Financial Sta- bility, 2015(17): 81 - 91.
5G.O.Karame, E.Androulaki, and S.Capkun.Dou- ble-spending fast payments in Bitcoin.Proceedings of the 2012 ACM Conference on Computer and Communi- cations Security[C]2012:906-917.
6S.Nakamoto. Bitcoin: A Peer-to-peer Electronic Cash System, Unpublished paper available at: http://bit- coing.org/bitcoin.pdf.