Simplify the following text for a Grade 11 native English-speaking person.
Original: The following is a complete ISO 3166-1 encoding code list in alphabetical order by the English short country names officially used by the ISO 3166 Maintenance Agency ( ISO 3166\/MA ) , which uses country names from United Nations sources .
Simplified: According to the ISO 3166 Maintenance Agency ( ISO 3166\/MA ) , the only way to enter a new country name into ISO 3166-1 is to have it registered in one of the following two sources :