Relatório e contas da comissão administrativa : exercícios de 1959/1960 / Cooperativa dos CTT S.C.R.L
Postal Laws and Regulations of the United States of America : Revised and edited in accordance with the act of confress approved February 23, 1931 / Walter F. Brown ( Postmaster General)
The postal Law : (english version) / Ministry of Communications Directorate General of Posts
Diccionario de la legislacion vigente de correos : [Espanha]