1. Gatewood, G., and Eichhorn, H. K.; 1973. Astron. J. 78, pp. 769-.
2. Gatewood, G., and Fredrick, L. W.; 1971. Conference on Photographic Astrometric Technique, NASA Contractor’s Report CR-1825, pp. 191–195.
3. Gould, B. A.; 1870. Mem. Nat. Acad. Sci. IV, pp. 193-.
4. Johnson, H. L.; 1952. Astrophys. J.116, pp. 640–648.
5. Russell, J. L.; 1976. The Astrometric Standard Region in Praesepe (M44), Ph.D. Dissertation, University of Pittsburgh, Pittsburgh, PA.