Fonte:
http://www.dgci.min-financas.pt/NR/rdonlyres/4E9F0BBE-E4AE-4F9D-B1E3-81EC35C87450/0/circ_023_05.pdf
http://www.dgci.min-financas.pt/NR/rdonlyres/5902CBE2-1AB0-4867-88AA-6927A88645C4/0/circ_069_07.pdf
