I dont know if it the right place to ask this type of question:
I am reading a book (De Gruyter Studies in Mathematics) Heinz Bauer, Robert B. Bruckel-Probability Theory. 23-Walter de Gruyter & Co (1996). Here I came up with a notation whose description I can't find in the book.
The Notation : $\cap$-stable sets.
Can someone explain me the notation?