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 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 Top 101 Mathematicians cover Top 101 Scientists cover Top 101 Women of STEM cover eggheads Guide to Algebra cover egghead?s Guide to Calculus cover