FQL query: query with multiple stream_id gives too few records

I would like to query public posts from multiple Pages.

My FQL query looks like this:

SELECT post_id, source_id FROM stream WHERE source_id in (157528807603192, 127531603328)

This query returns only about 6 records.

However, if I use the two source_id in two separate query I got more than 20 item for both of them:

SELECT post_id, source_id FROM stream WHERE source_id in = 157528807603192

I couldn't find anything in the documentation stating that if you query multiple source_id you need different permissions.

Can anyone explain me what is happening here?

I've found the answer in the documentation. :(

http://developers.facebook.com/docs/reference/rest/stream.get/

"If you specify only one user ID in the source_ids array, you can return, at minimum, the last 50 posts from that user's profile stream (Wall) for the last 180 days (it likely can be more).

If you specify more than one user ID in the source_ids array, you can return posts in those streams only from the last few days (about one week)."