1. Al-Obaidan, A.M., Scully, G.W. (1991), “Efficiency differences between private and state-owned enterprises in the international petroleum industry”, Applied Economics, Vol. 23, No. 2, pp. 237-246.
2. Al-Mazeedi, W. (1992), “Privatizing the national oil companies in the Gulf”, Energy Policy, Vol. 20, No. 2, pp 983-994.
3. Amit, R.H., Zott, C., Massa, L. (2010), The Business Model: Theoretical Roots, Recent Developments, and Future Research, University of Navarra: Pamplona, Spain.
4. Boscheck R. (2006), “Assessing “New” Upstream Business Models”, IMD International, available at: https://www.imd.org/research/publications/upload/Boscheck_WP_2006_6_Level_1.pdf, [Accessed 20 February, 2016].
5. Bruns, S.B. (2014), “German energy suppliers from the perspective of business model dynamics”, University of Twente, available at: http://essay.utwente.nl/65397/ [Accessed 20 February, 2016].