https://vocabularyserver.com/unesco/en/https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846Reference materials https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Books BT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Reference services RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Indexes RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Directories RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Bibliographies RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Atlases RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Thesauri RT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Encyclopaedias NT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Dictionaries NT https://vocabularyserver.com/unesco/en/xml.php?skosTema=4846 Reference works UF