Santana Hunt 
El ciclo del nitrógeno (The Nitrogen Cycle) [PDF ebook] 

There are many steps in the nitrogen cycle that include difficult concepts and words: denitrification, prokaryotes, ammonia, and more. With the help of this understandable book, even struggling readers will grasp this cycle of nature. Low-level language, fact boxes, and an extended glossary provide readers with essential vocabulary explanations that allow them to further understand each step of the cycle. Full-color diagrams aid readers” comprehension as they move through the cycle from start to finish, and then around again.