Fonte: http://www.dgaiec.min-financas.pt/NR/rdonlyres/92DE9AAD-8F7A-4796-8791-D98ED4AE83F6/0/Circular_n_55_2008_II.pdf
http://www.dgaiec.min-financas.pt/NR/rdonlyres/0F6C258A-842F-4909-B947-0767FF5B6363/0/Circular_n__56__2008_II.pdf
