Constraint_programming_libraries_for_imperative_programming_languages Constraint_programming

^ frédéric benhamou; narendra jussien; barry o sullivan (2007). trends in constraint programming. john wiley , sons. p. 45. isbn 978-1-905209-97-2. 
^ francesca rossi; peter van beek; toby walsh (2006). handbook of constraint programming. elsevier. p. 157. isbn 978-0-444-52726-4.