Chernyi, A. V., and A. I. Yakimchik. “Recovery of Potential Using Module Values of Its Gradient. 1”. Geofizicheskiy Zhurnal, vol. 21, no. 3, Apr. 1999, pp. 55-72, doi:10.24028/gzh.0203-3100.v21i3.1999.214577.