Fonte:
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/D81E6B00-B5BE-4822-82C4-4DCEDC2509D7/0/OficCirc_30112.pdf
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/A5C24008-191A-4AC6-987B-E07577C64AA1/0/OficCirc_30113.pdf
