National Drug File - Reference Terminology Exposure Ontology Source
http://purl.bioontology.org/ontology/STY/T024 http://purl.obolibrary.org/obo/ExO_0000045 LOOM
http://purl.bioontology.org/ontology/STY/T025 http://purl.obolibrary.org/obo/ExO_0000046 LOOM