1. The Office of Technology Assessment. Patent-term extension and pharmaceutical industry. 1981. Available: http://www.fas.org/ota/reports/8119.pdf. Accessed 25 April 2015.
2. Appropriating the returns from industrial research and development;RD Levin;Brookings Pap Econ Act,1987
3. Cohen W, Nelson RR, Walsh JP. Protecting Their Intellectual Assets: Appropriability Conditions and Why U.S. Manufacturing Firms Patent (or Not): National Bureau of Economic Research; 2000. Available: http://www.nber.org/papers/w7552.pdf. Accessed 25 April 2015.
4. Analysis of the impact of the Uruguay Round Agreements Act on pharmaceutical patents;E Seoane-Vazquez;Food Drug Law J,2009