1. Ambec, S., A.M. Cohen, S. Elgie, and P. Lanoie. 2013. The porter hypothesis at 20: Can environmental regulation enhance innovation and competitiveness? Review of Environmental Economics and Policy 7(1): 1–22.
2. Andersen, R.S. 2015. Bergen Havn gir halv pris til miljøvennlige skip,
http://www.sysla.no/2015/06/10/maritim/bergen-havn-gir-halv-pris-til-miljovennlige-skip_51794/
(accessed June 17 2015).
3. Carrillo-Hermosilla, J., P. del Río González, and T. Könnölä. 2009. Eco-innovation: When sustainability and competitiveness shake hands. London: Palgrave Macmillan.
4. Cleff, T., and K. Rennings. 2012. Are there any first-mover advantages for pioneering firms? European Journal of Innovation Management 15(4): 491–513.
5. Cohen, B., and M.I. Winn. 2007. Market imperfections, opportunity and sustainable entrepreneurship. Journal of Business Venturing 22: 29–49.