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2. Becker R., Betzold K., Boness K.D., Collings R., Holt G.G., Simkin J., “The Modelling of Electrical Current NDT Methods and its Application to Weld Testing”, IIW-Document V-792–85
3. “Analytical Solutions to Eddy Current Probe Coil Problems”;Dodd;Journal of Applied Physics,1968
4. Betzold K., Becker R., “Ergebnisse vom Einsatz eines neuartigen Mehrfrequenz-Wirbelstrom-Geräteprototyps an Dampferzeugerrohren mit rechnergestützter Systemauslegung”, Proceedings of the 12th MPA-Seminar “Safety and Reliability of Pressure Components”, Oct. 1986