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

Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S.
Start: 01-Jan-2019
End: 14-Nov-2022
SDFE, The Danish Agency, 2007, Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/9XPY-9A11

Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S.
Start: 14-Aug-2007
End: 31-Dec-2011
Bevis, Michael, 2007, Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T52V2D6G

Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S.
Start: 14-Aug-2007
End: 14-Nov-2022
SDFE, The Danish Agency, UNAVCO Community, Bevis, Michael, 2007, Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5PH-B743

Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S.
Start: 01-Jan-2012
End: 31-Dec-2018
UNAVCO Community, 2007, Greenland GNSS Network - NNVN-North Niviarsiat Nunatak P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/C1H4-9E98