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

Geopentech GPS Network - CASE-CaseSpgsFSCA2013 P.S.
Start: 06-Dec-2013
End: 13-Dec-2021
Walls, Chris, 2013, Geopentech GPS Network - CASE-CaseSpgsFSCA2013 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T54M92N1

Geopentech GPS Network - CASE-CaseSpgsFSCA2013_1HZ P.S.
Start: 07-Jan-2014
End: 14-Dec-2021
Walls, Chris, 2014, Geopentech GPS Network - CASE-CaseSpgsFSCA2013_1HZ P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5N014S2