This name is a synonym of Juncus alpinoarticulatus subsp. rariflorus (Hartm.) Holub.
The record derives from IOPI
(data supplied on 2012-03-23)
which reports it as a synonym (record 314330) with original publication details: Fl. Great Britain Ireland 5: 363 1996.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:995176-1.
This name was in version 1 of The Plant List, record kew-314330.