U.S. National Report to International Union of Geodesy and Geophysics 1991 - 1994. Contributions in Dynamics of the Solid Earth and Other Planets, ed. by R. A. Pielke, Washington, D.C., American Geophysical Union, vol. C 560, 183 pp., no. AFGL-TR-88-0314, pp. 413-418, (ISBN 3-933346-037)