author = { Hopenhayn, Hugo A. National Bureau of Economic Research Mitchell, Matthew F. },

title = { Innovation Fertility and Patent Design },

publisher = {National Bureau of Economic Research},

year = {April 1999},

booktitle = {NBER working paper series ; no. w7070},

address = { Cambridge, Mass },

url = { http://slubdd.de/katalog?TN_libero_mab2 }