Juvenile literature History 13 Nutrition 11 Biography 7 Experiments 6 Food 6 Miscellanea 6 Human anatomy 5 Human physiology 5 Aeronautics 4 Children 4 Diet 4 Health 4 Medicine 4 Technology 4 Airplanes 3 Beverages 3 Body, Human 3 Design and construction 3 Fruit 3 Human body 3 Inventions 3 Meat 3 Skeleton 3 Vocational guidance 3 Wheels 3 Accidents 2 Airplanes, Military 2 Armored vehicles, Military 2 Artificial satellites 2