Fonte:
http://www.pwc.com/pt/en/pwcinforfisco/noticias/imagens/IVA-ofcirc_30125.pdf.
http://info.portaldasfinancas.gov.pt/NR/rdonlyres/5113C68A-8F1B-491C-8ECD-D116CC8E434F/0/IVA-of%20circ%2030126.pdf
