See e.g. p. 201, The Binary Stars, Robert Grant Aitken, Semicentennial Publications of the University of California, 1918, or Format, Sixth Catalog of Orbits of Visual Binary Stars, William I. Hartkopf & Brian D. Mason, U. S. Naval Observatory, Washington, D.C. Accessed on line October 25, 2008
navy.mil
ad.usno.navy.mil
See e.g. p. 201, The Binary Stars, Robert Grant Aitken, Semicentennial Publications of the University of California, 1918, or Format, Sixth Catalog of Orbits of Visual Binary Stars, William I. Hartkopf & Brian D. Mason, U. S. Naval Observatory, Washington, D.C. Accessed on line October 25, 2008
