Can't filter references with multiple types

[aeturneus]

It appears that filter is supposed to be a way to exclude specific types of items from the "gather references" list. However, I can't get it to exclude multiple types. I want my references list to only populate with assets and certain types of documents, instead I get hundreds of other references that never need to be duplicated.

Have I misunderstood the purpose of filter or can you provide example syntax for excluding multiple item types from the "gather references" list?