An "apostille" is a form of authentication issued to documents for use in countries that participate in the Hague Convention of 1961. A list of countries that accept apostilles is provided by the US State Department.
Step 1: Mail-in your original Certificate of Naturalization document or a certified true copy by UCIS to our Washington D.C. office for processing...
Step 2: International Apostille will verify and process your document through the U.S. Department of State in Washington, DC in four business days.
Go Here: https://www.internationalapostille.com/apostille-a-certificate-of-naturalization/