Union set: The set whose elements belong to A or B is called the union (set) of A and B, marked as A∪B (or B∪A), and pronounced as A and B (or B and A), that is, A∪B={x|x∈A, or X.

Intersection:? A set with elements belonging to A and B as elements is called the intersection (set) of A and B, marked as A∩B (or B∩A) and pronounced as "A across B" (or "B across A"), that is, A∩B={x|x∈A, X ∈.

As for your collection, I don't know. I haven't studied it, and I haven't found it online. Do you remember wrong? Or is it renamed now? You mean the complete works?

More about the collection has been linked.