The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

HOPRnet GPS Network - ALFD-Alftadalur P.S.
Start: 21-Oct-2014
End: 17-Oct-2019
Grapenthin, Ronni, 2016, HOPRnet GPS Network - ALFD-Alftadalur P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/QEF6-7508