found: Work cat.: Price, D. Pillwort (Pilularia globulifera), 2006.
found: Missouri Botanical Garden Tropicos database, accessed online 11 Jan. 2010(Pilularia globulifera, family Marsileaceae)
found: Interactive Flora of NW Europe, accessed online 11 Jan. 2010(Pillwort, scientific name Pilularia globulifera; family Marsileaceae)
found: Wikipedia, 11 Jan. 2010:under Pilularia (Pilularia globulifera, or pillwort, is native to western Europe, where it grows at edges of lakes, ponds, ditches and marshes ...)
notfound: ITIS database