Kipp, R.M., M. McCarthy, A. Fusaro, and I.A. Pfingsten, 2020, Nitellopsis obtusa (Desvaux in Loiseleur) J. Groves, (1919): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/GreatLakes/FactSheet.aspx?SpeciesID=1688, Revision Date: 1/15/2020, Peer Review Date: 11/12/2012, Access Date: 2/24/2020