Fonte:
http://www.dgaiec.min-financas.pt/NR/rdonlyres/9004FD56-B265-423C-A148-5EED93BAE483/0/Circular_n_90_2008_II.pdf
http://www.dgaiec.min-financas.pt/NR/rdonlyres/367BE42F-7D5F-4C12-84A8-9DA10C6D4A12/0/Circular_n_91_2008_II.pdf
http://www.dgaiec.min-financas.pt/NR/rdonlyres/ADCD0ADA-5A43-41B1-8F08-52CC2D33D925/0/Circular_n_92_2008_II.pdf
