<ul><li><a href=http://www.pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=253&tabela=leis target=_blank>Decree-Law 398/1998 of the General Tax Law( Decreto-Lei da Lei Geral Tributária, Adopted 17/12/1998, Last modification 31/03/2020, Article 19.6)</a></li><li><a href=https://dits.deloitte.com/#TaxGuides target=_blank>Deloitte International Tax Portugal Highlights 2019(Last consulted on 28/07/2020)</a></li></ul>