641
by Cunningham
Published 2010
642
by Fisher
Published 2008
643
by Ben-Naim
Published 2008
644
by Halmos
Published 1995
645
by Wilde
Published 2006
646
by Ho-Kim
Published 2004
647
by Applegate
Published 2011
648
by Stone
Published 2009
649
by Laub
Published 2005
650
by Blum
Published 2006
651
by Golub
Published 1996
652
by Sumner
Published 2005
653
by Langan
Published 2011
654
by Khoshafian
Published 2007
655
by Tidwell
Published 2008
656
657
by Swisher
Published 2005
658
by Vaughn
Published 2010
659
by Poikselka
Published 2009
660
by James
Published 2009