Useful websites
Useful books
All taxonomical guides published by the Freshwater Biological Association (see link)
Oscoz, J., Galicia, D. & Miranda, R. (eds.) (2011) Identification Guide of Freshwater Macroinvertebrates of Spain. Springer, Switzerland.
Tachet, H., Richoux, P., Bournaud, M. & Usseglio-Polatera, P. (eds.) (2010) Invertébrés d'Eau Douce: Systématique, Biologie, Écologie. Freshwater Invertebrates: Systematics, Biology, Ecology. 2nd edition. Centre National de la Recherche Scientifique, Paris.
Nilsson, A. (ed.) (2005) Aquatic Insects of North Europe. A Taxonomic Handbook. Volumes 1 and 2. Apollo Books, Vester Skerninge (Denmark).
Böcher, J., Kristensen, N.P., Pape, T. & Vilhelmsen, L. (eds.) (2015) The Greenland Entomofauna. An Identification Manual of Insects, Spiders and their Allies. Fauna Entomologica Scandinavica. Volume: 44. Brill, Leiden (the Netherlands).
Free resources
World
Africa
Gerber, A. & Gabriel, M.J.M. (2002) Illustrations from A guide to the identification of aquatic invertebrates in South African Rivers