I found that "Entertainment book" timed out, but using "Entertainment" and "Discount" together worked and had fewer off-topic threads. While it can be a pain to sift through a lot of results, one word searches seem to work most all of the time. Here are a couple more if you care to look (though the one nako listed will probably answer all your questions):

http://www.flyertalk.com/forum/showt...nment+discount

http://www.flyertalk.com/forum/showt...nment+discount