Alternative Energy cover Astronomy: Understanding the Universe cover Dinosaur cover Dinosaurs: A Visual Encyclopedia cover Earth and Its Moon cover Everything You Need to Know about Snakes and Other Scaly Reptiles cover Human Body: A Visual Encyclopedia cover My Tourist Guide to The Prehistoric World cover My Tourist Guide to the Center of the Earth cover Plant, Rev. ed. cover Pond & River, Rev. ed. cover Predator cover Seasons cover The Inner Planets: Mercury, Venus, and Mars cover The Nature of Planets, Dwarf Planets, and Space Objects cover The Outer Planets: Jupiter, Saturn, Uranus, and Neptune cover The Sun, Stars, and Galaxies cover Water cover eggheads Guide to Algebra cover egghead?s Guide to Calculus cover