Original: The 12-volume Micropædia is one of the three parts of the 15th edition of Encyclopædia Britannica, the other two being the one-volume Propædia and the 17-volume Macropædia.
Simplified: The 12-book Micropædia is one of the three parts of the 15th edition of Encyclopædia Britannica, and the other two being the one-book Propædia and the 17-book Macropædia.