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

Greenland GNSS Network - SMM2-SummitCanpGL2013 P.S.
Start: 08-Jul-2013
End: 24-Jul-2020
UNAVCO Community, 2014, Greenland GNSS Network - SMM2-SummitCanpGL2013 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T56D5RRP