@techreport{NBERw13644,
 title = "Patents, Thickets, and the Financing of Early-Stage Firms: Evidence from the Software Industry",
 author = "Iain M. Cockburn and Megan MacGarvie",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "13644",
 year = "2007",
 month = "November",
 URL = "http://www.nber.org/papers/w13644",
}