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

Greenland GNSS Network - SUMM-Summit Camp, Greenland P.S.
Start: 25-Apr-2006
End: 30-Jun-2009
UNAVCO Community, 2006, Greenland GNSS Network - SUMM-Summit Camp, Greenland P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5B56HHV