10 scientific keys from the freshwater biological association in the 1970s free to any budding freshwater enthusiasts. Titles are:
5 - Cladocera - water fleas
13 - Gastropods - snails
15 - Ephemeroptera adults (mayflies)
16 - Water Bugs
17 - Stoneflies
18 - Cyclopid and calanoid copepods
20 - Ephemeroptera nymphs (mayflies)
22 - Aquatic oligochaeta (earthworms)
24 - Simuliidae (black flies)
26 - Eliminthidae (water beetles)