Hippuris tetraphylla USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 613.

Hippuris vulgaris Robert H. Mohlenbrock USDA-NRCS PLANTS Database / USDA NRCS. 1992. Western wetland flora: Field office guide to plant species. West Region, Sacramento. - Not copyrighted image

Hippuris vulgaris Credit: Photo by Leo Michels. Usage: Public Domain