@prefix skos:	<http://www.w3.org/2004/02/skos/core#> .
@prefix isac:	<http://webisa.webdatacommons.org/concept/> .
isac:volume_hologram_	skos:broader	isac:diffraction_structure_ .
isac:relief_structure_	skos:broader	isac:diffraction_structure_ .