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2. Balsley Jr., J. R., seeRumbaugh, L. H. Trans. Am. Geoph. Union, 30, No. 6 etc —Brewer, A. W. & Jarman, C. A., U. S. patent 2, 606, 229 (1952).
3. Davids, N., seeVestine, E. H. Terr. Mag., 50, No. 1 etc. —Eötvös, R., Aus dem 1. Band der Abhandl. der XV. Allg. Konferenz der Erdmessung in Budapest 1906 (1907).
4. Garland, G. D., Canadian Min. Met. Bull., 44, No. 472, p. 546–551 (1951).
5. Garland, G. D., Geophysics, XVI, No. 1 (1951).