8 (b) Works by a National Artist; Unless declared by the National Museum, (c) Archaeological and traditional ethnographic materials; Unless declared by the National Historical Institute, (d) Works of national heroes; (e) Marked structure; (f) Structures dating at least fifty (50) years old; and Unless declared by the National Archives, (g) Archival material/document dating at least fifty (50) years old. The property owner may petition the appropriate cultural agency to remove the presumption of important cultural property which shall not be unreasonably withheld. SEC. 6. World Heritage Sites. - The appropriate cultural agency shall closely collaborate with the United Nations Educational Scientific and Cultural Organization (UNESCO) National Commission of the Philippines in ensuring the conservation and management of world heritage sites, of cultural and mixed sites category, in the Philippines. SEC. 7. Privileges for Cultural Property. - All cultural properties declared as national cultural treasures and national historical landmarks, sites or monuments shall be entitled to the following privileges: (a) Priority government funding for protection, conservation and restoration; (b) Incentive for private support of conservation and restoration through the Commissions Conservation Incentive Program for national cultural treasures; (c) An official heritage marker placed by the cultural agency concerned indicating that the immovable cultural