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

Southern Basin and Range GPS Network - SMYC-Spring Mountain Youth Camp P.S.
Start: 23-Mar-1999
End: 21-Mar-2011
Wernicke, Brian P., 1999, Southern Basin and Range GPS Network - SMYC-Spring Mountain Youth Camp P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5VH5M5B