D. Dinh Ang, V. Thanh Nhieu, and D. Ngoc Thanh, “IDENTIFICATION OF MASS ONHOMOGENEITY FROM GRAVITY ANOMALIES & LINEARIZATION AND REGULARIZATIO: BY MOMENT PROBLEMS”, VNUHCM Journal of Science and Technology Development, vol. 6, no. 3&4, pp. 5-7, Apr. 2003.