Russell, Henry Norris (June 1944). "Notes on white dwarfs and small companions". The Astronomical Journal51: 13. doi:10.1086/105780. Bibcode: 1944AJ.....51...13R.
Russell, Henry Norris (June 1944). "Notes on white dwarfs and small companions". The Astronomical Journal51: 13. doi:10.1086/105780. Bibcode: 1944AJ.....51...13R.