'Appendix 2 - List of ITU-T recommendation E.164 assigned country codes' (Telecommunications, 2017), 'Understanding Telecommunications Networks, (2nd Edition)', Chap. appendix2, pp. 363-367, DOI: 10.1049/PBTE071E_appendix2 IET Digital Library, https://digital-library.theiet.org/;jsessionid=69cvpqcrcsijc.x-iet-live-01content/books/10.1049/pbte071e_appendix2