Fonte:
http://www.dgaiec.min-financas.pt/NR/rdonlyres/B2F93DB4-43D2-4A39-96C9-CA941024FEA6/0/Circular_n_118_2009_II.pdf~
http://www.dgaiec.min-financas.pt/NR/rdonlyres/097733D7-60EE-4EA8-A530-C8B35577CD9A/0/Circular_n_117_2009_II.pdf
