abstract = "In steady state Twin GP both children created by
sub-tree crossover and point mutation are used. They
are born together and die together. Evolution is little
changed. Indeed fitness selection using the twin's
co-conceived doppelganger is possible.",
notes = "C code for twin GP is available via via
http://www.cs.ucl.ac.uk/staff/W.Langdon/ftp/gp-code/tiny_gp_twin.c