Grechenig, Kristoffel Max Planck Institute for Research on Collective Goods, Max Planck Society;
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1946760 (Any fulltext)
http://www.coll.mpg.de/pdf_dat/2011_24online.pdf (Preprint)
Grechenig, K., & Kolmar, M. (2011). The State’s Enforcement Monopoly and the Private Protection of Property.