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

GGN GPS Network - RIOP-Riobamba P.S.
Start: 10-Jun-1996
End: 14-Nov-2022
Mothes, Patricia A., Jarrin, Paul, 1997, GGN GPS Network - RIOP-Riobamba P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5WM1BN4