Koch, M. 1986. “Nonlinear Inversion of Local Seismic Travel Times for the Simultaneous Determination of the 3D-Velocity Structure and Hypocentres - Application to the Seismic Zone Vrancea”. Journal of Geophysics 56 (1), 160-73. https://journal.geophysicsjournal.com/JofG/article/view/240.