Peter A. Moldovyanu E. Dernova A. Kostina Nick A. Moldovyan Multisignature Protocols and Problem of Simultaneous Signing a Package of Contracts. 331-341 2009 IF&GIS http://dx.doi.org/10.1007/978-3-642-00304-2_23 conf/ifgis/2009 db/conf/ifgis/ifgis2009.html#MoldovyanuDKM09