Fonte:
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/4CF602FA-27CF-4F23-9E2C-6C33A149F1B5/0/OficCirc_90016.pdf
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/8B0083B5-0652-4018-935B-2610A9E1753E/0/OficCirc%2030117.pdf
