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

Costa Rica GPS Network - IRZU-Irazu P.S.
Start: 08-Dec-1999
End: 23-May-2003
Schwartz, Susan, 2000, Costa Rica GPS Network - IRZU-Irazu P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5639MTB