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

MAGNET - GARR-GARR P.S.
Start: 06-Jul-2006
End: 02-May-2018
Blewitt, Geoff, Hammond, William C., Kreemer, Corne, 2009, MAGNET - GARR-GARR P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5S46Q43