Bessel, F. W. (1844c). «On the variations of the proper motions of Procyon and Sirius». Monthly Notices of the Royal Astronomical Society6 (11): 136–141. doi:10.1093/mnras/6.11.136a. Bibcode: 1844MNRAS...6R.136B.
Bessel, F. W. (1844c). «On the variations of the proper motions of Procyon and Sirius». Monthly Notices of the Royal Astronomical Society6 (11): 136–141. doi:10.1093/mnras/6.11.136a. Bibcode: 1844MNRAS...6R.136B.