Anh, N. T. L., N. T. M. Hanh, H. M. Anh, and N. P. Tuan. “Responsibility and Authority in Management of Overseas Upstream Investment and Application for Petrovietnam”. Petrovietnam Journal, Vol. 7, July 2013, pp. 48-5, http://www.tapchidaukhi.vn/index.php/TCDK/article/view/691.