Wambsganss, Joachim (August 31, 2001). "Gravitational Lensing in Astronomy". Living Reviews in Relativity. Max Planck Institute for Gravitational Physics (Albert Einstein Institute). Archived from the original on April 10, 2016. "Today such a lens configuration is called 'Einstein-ring', although more correctly it should be called 'Chwolson-ring'."
Wambsganss, Joachim (August 31, 2001). "Gravitational Lensing in Astronomy". Living Reviews in Relativity. Max Planck Institute for Gravitational Physics (Albert Einstein Institute). Archived from the original on April 10, 2016. "Today such a lens configuration is called 'Einstein-ring', although more correctly it should be called 'Chwolson-ring'."