>Thank you for the reference. Reading through the paper it >seems that a double bar above a set, for example >= >A >means the cardinality of the set, the cardinality of A for example. > >What I don't understand is what > >== >EU > >means in the paragraph between the statement of the theorem >and the fist lemma. If E is a set and U an open ball, then >what does EU mean?
My immediate guess (without bothering to look at the actual paper) is that it's the old notation (i.e., juxtaposition) for "set product", the old phrase for intersection. Except in French of course.