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

Peatland Minnesota GPS Network - FEN0-Fen Site P.S.
Start: 01-Jul-1997
End: 21-May-2012
Glaser, Paul, 1999, Peatland Minnesota GPS Network - FEN0-Fen Site P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T51J9828