1. Corbin Th.E., Observing the Astrometric Reference Stars at the US Naval Observatory,this Vol.
2. Corbin Th.E., Urban S.E., A Catalog of Reference Stars for New Reductions of the Astrographic Catalog Plates,this V.
3. de Vegt. Chr., 1974, IAU Symposium 61, 209
4. de Vegt. Chr., 1978, CDS-Inf. Bull. 15, 51
5. de Vegt. Chr., 1979, IAU Coll. 48, Modern Astrometry, F. Prochazka, R. H. Tucker ed., p. 527