James Trefil, The Dark Side of the Universe, Anchor Books, 1989, pp. 55-56 "The prpblem of explaining the existence of galaxies has proved to be one of the thorniest in cosmology. By all rights, they just shouldn't be there, yet there they sit. It's hard to convey the depth of frustration that this simple fact induces among scientists. Time after time, new developments have come along and it has seemed that the problems was solved. Each time the solutution turned soft, new problems developed, and we werer right back where we started."