Qin Jiushao wrote The Shushu Jiuzhang. In chapter one of this text he discusses the Chinese remainder theorem. Chapter 2 is sometimes called the heavenly phenomena chapter because it deals with questions about the calendar as well as snow and rain. Chapter 3 was boundaries of fields, looking at questions dealing with the study of surveying. Chapter 4 is Telemetry, looking at the distance to or between points that are not accessible.