9780761422013 | Benchmark Books, September 25, 2006, cover price $7.20 | About this edition: Introduces the element of molybdenum, discussing its physical and chemical properties, where it is found, and what processes or objects it is used in.
9780761419204 | Benchmark Books, September 30, 2005, cover price $7.20 | About this edition: Discusses chromium and where it can be found, how it was discovered, its special characteristics, and its importance to the human body.