<http://ns.inria.fr/covid19/PMC3853722#body_text>	<http://purl.org/dc/terms/subject>	"Physical chemistry" .
<http://ns.inria.fr/covid19/PMC3853722#body_text>	<http://purl.org/dc/terms/subject>	"Aircraft first flown in 1991" .
<http://ns.inria.fr/covid19/PMC3853722#body_text>	<http://purl.org/dc/terms/subject>	"April observances" .