<http://webisa.webdatacommons.org/138191333>	<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>	<http://www.w3.org/ns/prov#Entity> .
<http://webisa.webdatacommons.org/138191333>	<http://www.w3.org/ns/prov#wasQuotedFrom>	<nih.gov> .
<http://webisa.webdatacommons.org/prov/388800790>	<http://www.w3.org/ns/prov#wasDerivedFrom>	<http://webisa.webdatacommons.org/138191333> .
<http://webisa.webdatacommons.org/138191333>	<http://www.w3.org/ns/prov#value>	"Changes and errors in email addresses, email filtering programs and other factors make it impossible to report how many of the invitations were read by the person they were addressed to." .