Fonte:
http://www.dgci.min-financas.pt/NR/rdonlyres/F4863622-1713-488B-9721-91BB185B3B6C/0/Circular5_2007.pdf
http://www.dgci.min-financas.pt/NR/rdonlyres/0EA65AE9-856A-4607-8FCD-DB31784E863B/0/Circular6_2007.pdf
