http://www.google.com/url?sa=D&q=http://www.anatel.gov.br/Tools/frame.asp%3Flink%3D/acontece_anatel/palestras/portabilidade_numerica.pdf
http://www.google.com/url?sa=D&q=http://www.anatel.gov.br/Tools/frame.asp%3Flink%3D/biblioteca/resolucao/1998/anexo_res_86_1998.pdf