1. Tela botanica: http://www.tela-botanica.org/bdtfx-nn-48329-synthese
2. International Plant Names Index (IPNI): http://www.ipni.org/ipni/simplePlantNameSearch.do?find_wholeName=Persicaria% 20hydropiper&output_format=normal&query_type=by_query &back_page=query_ipni.html
3. The plant list: http://www.theplantlist.org/tpl/search?q=Persicaria %20hydropiper
4. Integrated Taxonomic Information System: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value= 518732#null
5. http://manche-nature.fr/wp-content/uploads/2016/05/Persicariahydropiper-2.jpg