Before you can submit official U.S. documents (issued by the U.S. authorities or notarized by U.S. public notaries) to Latvia's official institutions, they have to be authorized with a special apostille certification. Usually you can obtain the apostille certification in the Offices of the Secretary of State where the document originally was issued or notarized. The certification is requested in accordance with the Convention Abolishing the Requirement of Legalization for Foreign Public Documents (concluded October 5, 1961) http://hcch.e-vision.nl/index_en.php?act=conventions.text&cid=41 For detailed information on how and where to authorize your U.S. documents, visit http://travel.state.gov/about/authentication.html.