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

PBO GPS Network - AB53-CrystalMtnAK2011 P.S.
Start: 28-Jul-2011
End: 30-Aug-2021
UNAVCO Community, 2011, PBO GPS Network - AB53-CrystalMtnAK2011 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5W37TB0