http://www.planalto.gov.br/ccivil_03/leis/l8666cons.htm

http://www.planalto.gov.br/ccivil_03/decreto/2001/D3931htm.htm

http://www.planalto.gov.br/ccivil_03/leis/2002/l10520.htm

http://www.planalto.gov.br/ccivil_03/decreto/d3555.htm

http://www.planalto.gov.br/ccivil_03/_Ato2011-2014/2013/Decreto/D7892.htm

http://www.planalto.gov.br/ccivil_03/leis/l4320compilado.htm

http://www.receita.fazenda.gov.br/Legislacao/LeisComplementares/2006/leicp123.htm

http://www.planalto.gov.br/ccivil_03/_ato2004-2006/2005/decreto/d5450.htm