22 http://setiathome.berkeley.edu/index.php 23 http://beamartian.jpl.nasa.gov/welcome 24 http://fold.it/portal/ 25 http://www.birds.cornell.edu/pfw/ 26 http://www.cocorahs.org/ de Vaucouleurs (1991)

by M Davis, P Guhathakurta, N P Konidaris