Jens Christian Schou & Bjarne Moeslund 
Key to the Aquatic Plants of Northern and Central Europe including Britain and Ireland [PDF ebook] 

Jens Christian Schou is a botanist, illustrator and photographer who specializes in Nordic plants.
Bjarne Moeslund is an environmental consultant who led the creation of the first guide to Denmark’s aquatic plants and was later coauthor of a more comprehensive book on the subject.
Klaus van de Weyer is a freshwater ecologist and botanist, an expert on macrophytes and an underwater photographer who teaches classes on macrophyte ecology and identification.
Richard V. Lansdown works in wetland conservation, has surveyed macrophytes in rivers throughout Britain and Ireland and teaches courses on aquatic plant identification.
Gerhard Wiegleb is professor emeritus of general ecology at Brandenburg University of Technology Cottbus and a widely published expert on macrophyte ecology.
Peter Holm is an expert on the identification of macro invertebrates and aquatic plants in rivers, streams and lakes.
Lars Baastrup-Spohr is assistant professor in freshwater ecology at the University of Copenhagen.
Kaj Sand-Jensen is professor of freshwater ecology at the University of Copenhagen and the author of books and popular science articles on Danish nature.