1. Accessibility Metadata. http://schema.org/accessibilityFeature
2. Accessibility Metadata Project. http://www.a11ymetadata.org/
3. Accessibility Vocabularies in Multimodal User Interfaces. http://homepages.cwi.nl/~media/ontologies/multimodality.owl
4. ACCESSIBLE ontology. http://www.accessible-eu.org/index.php/ontology.html
5. AccessOnto ontology. http://shapevle.canterbury.ac.uk/repository/AccessOnto.xml