General encyclopaedias cover all the existing branches of human knowledge. They are most popular and extensively used reference sources. They are classified into different categories as per the format, coverage, user's age, and language. Some popular examples are mentioned below.
a) Comprehensive Multi-Volume Encyclopaedia for Adults. - English Language
b) Popular Multi-volume Encyclopaedia for Adults
c) Multi-volume Encyclopaedias for Junior and Children
d) One and Two Volume Adult and Junior Encyclopaedia
e) National and Regional Encyclopaedias