Occam's Inversion is an approach to the regularized inversion of nonlinear problems, first introduced in 1987 for the 1D resistivity and MT problems, but which has since found broad application in geophysics. One of the most popular current implementations is for the 2D MT problem.
"a heuristic algorithm, lacking theoretical underpinnings, but one that has been found to be remarkably effective in practice" (Bob Parker in Geophysical Inverse Theory)
The primary reference is:
Constable, S.C., R.L. Parker, and C.G. Constable, 1987: Occam's Inversion: a practical algorithm for generating smooth models from EM sounding data, Geophysics, 52, pp. 289-300.