The Drug Ontology	Material Element	Source
http://sweet.jpl.nasa.gov/2.3/matrElement.owl#Chalcogen	http://purl.obolibrary.org/obo/CHEBI_33303	LOOM
http://sweet.jpl.nasa.gov/2.3/matrElement.owl#Halogen	http://purl.obolibrary.org/obo/CHEBI_24473	LOOM