Grade 4

First mentioned in writings over 2,000 years ago, the lost city of Atlantis continues to puzzle people today. Some people doubt that it ever existed. Others claim that it was real, and that… More →

A medium-lift assault helicopter, CH-46 Sea Knights are used to deliver heavily armed troops into battle. They are also used on several other missions. Readers will learn about these large… More →

Indy cars are open wheel race cars that are used in the Indy Racing League (IRL). The cars speed along tracks with straight stretches and sharp turns. Safety is a large concern, as Indy car… More →

Thousands of people around the world have claimed to have been abducted by aliens. Is there truth to these reports, or did the people make them up in order to get into the headlines? This… More →

The first shapes found in crop fields were circles. Since then, people have discovered more complex designs. Where do these designs come from? Are they messages from alien visitors, or are… More →

Motorcycle drag racing is becoming a very popular motor sport. Amateur racers use their street bikes to drag race, while professionals use drag bikes that can reach 200 miles per hour.… More →

Denmark has consistently been ranked as one of the happiest countries in the world. It has a high standard of living, an impressive literacy rate, and an industrious economy. In this title,… More →

Used by the United States Army Special Forces, AH-6 Little Birds have a reputation for their ability to quickly attack a target and then get away before the enemy can react. They have proven… More →

Costa Rica, which means “Rich Coast,” is aptly named. Its long coastlines, bordering the Caribbean Sea to the east and the Pacific Ocean to the west, have some of the most diverse ecosystems… More →

This ancient country is considered the birthplace of Western civilization. Tourists can walk on the grounds of the first Olympic Games, see the mythical Mount Olympus, and visit the Acropolis More →

People have raced stock cars for almost a century. The technology has changed, but the excitement of the races has remained the same. This title explains the history of stock cars, what’s… More →

Famous for the snowy peaks of the Swiss Alps, Switzerland is a popular destination for skiing and snowboarding enthusiasts all over the world. Swiss alpine culture is also known for a long… More →