Fonte:
http://www.dgaiec.min-financas.pt/NR/rdonlyres/D9CD5ECA-163B-446B-A25A-28532748589F/0/Circular_n_90_2007_II.pdf
http://www.dgaiec.min-financas.pt/NR/rdonlyres/78EABB17-61CC-4DF0-B726-CDD02396830B/0/Circular_n_91_2007_II.pdf
