1. Auer, L.H., and van Altena, W.F.: 1978,Astron. J. 83, 531.
2. Dick, W., Hirte, S., Schilbach, E., and Scholz, R.-D.: 1988, InFundamentals of Astrometry, IAU Colloquium No.100, edited by H. Eichhorn, C.A., Murray, and A.R. Upgren,Celestial Mech. xx, yy. (this volume).
3. IAU Symposium;A.N. Deutsch,1974
4. Hanson, R.B.: 1987,Astron. J. 94, 409.
5. Klemola, A.R.: 1988, InFundamentals of Astrometry, IAU Colloquium No.100, edited by H. Eichhorn, C.A. Murray, and A.R. Upgren,Celestical Mech. xx, yy. (this volume).