Nature.com subject ontology EuroVOTech Astronomical Objects Source
http://scigraph.springernature.com/things/subjects/x-rays http://eurovotech.org/objects-structure.owl#XRays LOOM
http://scigraph.springernature.com/things/subjects/interstellar-medium http://eurovotech.org/objects-structure.owl#InterStellarMedium LOOM