Barban, M. B. "The Large Sieve Method and Its Application to Number Theory." Uspehi Mat. Nauk21, 51-102, 1966.Finch,
S. "Class Number Theory." http://algo.inria.fr/csolve/clss.pdf.
May 6, 2005.Sloane, N. J. A. Sequence A175640
in "The On-Line Encyclopedia of Integer Sequences."