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

Bhutan GPS Network - RBIT-Royal Bhutan Inst. of Tech. P.S.
Start: 24-Oct-2003
End: 30-Dec-2005
Bilham, Roger G., 2003, Bhutan GPS Network - RBIT-Royal Bhutan Inst. of Tech. P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5V40SJN