The following are included in the "free list" and are therefore free from any duties: "(516) Books, engravings, photographs, etchings, bound or unbound, maps and charts imported by authority or for the use of the United States or for the use of the Library of Congress. "(517) Books, maps, music, engravings, photographs, etchings, bound or unbound, and charts, which shall have been printed more than twenty years at the date of importation, and all hydrographic charts and publications issued for their subscribers or exchanges by scientific and literary associations or academies, or publications of individuals for gratuitous private circulation, and public documents issued by foreign governments. "(518) Books and pamphlets printed chiefly in languages other than English; also books and music, in raised print, used exclusively by the blind. "(519) Books, maps, music, photographs, etchings, lithographic prints, and charts, specially imported, not more than two copies in any one invoice, in good faith, for the use and by order of any society or institution incorporated or established solely for religious, philosophical, educational, scientific, or literary purposes, or for the encouragement of the fine arts, or the use and by order of any college, academy, school, or seminary of learning in the United States, or any state or public library, and not for sale, subject to such regulations as the Secretary of the Treasury shall prescribe. "(520) Books, libraries, usual and reasonable furniture, and similar household effects of persons or families from foreign countries, all the foregoing if actually used abroad by them not less than one year, and not intended for any other person or persons, nor for sale." {Sidenote: Library free importation} The provisions as to importation for libraries are made unnecessarily onerous by Treasury regulations intended to insure the identification of the actual copies so imported. In practice such copies are usually imported by library agents acting for the library and not only must these agents make oaths and present evidence of authorization from the library authorities, but the librarian must certify to the receipt of the individual copy, before it can be technically cleared from the custom house through which it is imported, and the importer relieved from further liability. Blank forms for these purposes are prescribed and provided by the Treasury Department. {Sidenote: Copyrights and the free list}