http://www.di.unipi.it/~andrea/GETGRATS/
http://www.di.unipi.it/~andrea/GETGRATS/getgrats.html#objectives

http://infolab.kub.nl/people/ademoor/papers/iccs97.pdf

http://citeseer.nj.nec.com/cache/papers/cs/20980/ftp:zSzzSzftp.dsv.su.sezSzuserszSzpajozSzer93.pdf/johannesson94using.pdf

http://www.graphtheory.com/contents.htm