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

BARGEN Expansion GPS Network - CLOV-Clover_CITNV2006 P.S.
Start: 16-Nov-2006
End: 20-Jul-2021
UNAVCO Community, 2006, BARGEN Expansion GPS Network - CLOV-Clover_CITNV2006 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/7SN2-6X31