Fonte:
http://www.dgaiec.min-financas.pt/NR/rdonlyres/86EFAD29-02A2-4898-9D1A-D76B51CEB825/0/Circular_n_66_2008_II.pdf
http://www.dgaiec.min-financas.pt/NR/rdonlyres/0DC8F40E-A823-4968-A7EA-3D156A6390E6/0/Circular_n_67_2008_II.pdf
