1. Fraser, D.C., 1969. Contouring of VLF-EM data. Geophysics 34, 958–967.
2. Fraser, D.C., 1981. A review of some useful algorithms in geophysics. Canadian Institute of Mining Transactions 74(828), 76–83.
3. Karous, M., Hjelt, S.E., 1977. Determination of apparent current density from VLF measurements: Report. Department of Geophysics, Univeristy of Oulu, Finland, Contribution No. 89, 19pp.
4. Linear filtering of VLF dip-angle measurements;Karous;Geophysical Prospecting,1983
5. Geological mapping using VLF radio fields;McNeill,1991