Fonte:
http://www.dgci.min-financas.pt/NR/rdonlyres/B120E306-FA0A-41A9-8017-421D460A3283/0/circ_017_01.pdf
http://www.dgci.min-financas.pt/NR/rdonlyres/49A2A3CF-A8EF-44A8-977C-6C560EC4FD42/0/cirs_086_01.pdf
