Magnificent knowledge base of fascinating subjects, in six volumes.
This series was first issued in 1975 as a weekly magazine in 120 parts. . It was later revised and re-issued (1991 and in 1995) in a loose-leaf format designed to be split up into individual sections for Human Body, Planet Earth, Science & Technology, Animals & Plants, World History etc. The second release in 144 issues is quite common but is a bit more difficult to offer in parts because the pages have usually been decollated and filed in the special ring binders designed to house it.
The whole series was revised again and re-issued in 1995 to bring it up to date for changes to the National Curriculum. This, the latest edition, has 192 parts.
June 2011