Baryonic Dark Matter - Google Books

http://books.google.de/books?id=DqAQX0D77ZYC&pg=PA179&lpg=PA179&dq=dark+matter+%22black+holes%22&source=bl&ots=SzFEHWOw1I&sig=pf

The visible universe is a small perturbation on the material universe. Zwicky and Sinclair Smith in the 1930s gave evidence of invisible mass in the Coma and Virgo Clusters of Galaxies. Better optical data has only served to confound their critics and the…