The following are useful papers on the subject of magnetotelluric data processing.


Gamble, T. D., Goubau, W. M., & Clarke, J. (1979). Magnetotellurics with a remote magnetic reference. Geophysics, 44(1), 53-68.


Jones, Alan G., et al. (1989). A comparison of techniques for magnetotelluric response function estimation. Journal of Geophysical Research: Solid Earth 94.B10 (1989): 14201-14213.


Egbert, G. D. (1997). Robust multiple-station magnetotelluric data processing. Geophysical Journal International, 130(2), 475-496.


Eisel, M., & Egbert, G. D. (2001). On the stability of magnetotelluric transfer function estimates and the reliability of their variances. Geophysical Journal International, 144(1), 65-82.


Smirnov, M. Y. (2003). Magnetotelluric data processing with a robust statistical procedure having a high breakdown point. Geophysical Journal International, 152(1), 1-7.


Chave, A. D., & Thomson, D. J. (2003). A bounded influence regression estimator based on the statistics of the hat matrix. Journal of the Royal Statistical Society: Series C (Applied Statistics), 52(3), 307-322.