Board Thread:General Discussion/@comment-75.85.13.233-20140203162755/@comment-69.172.146.177-20140203163533

Tap the card then tap the picture of a book on the upper right. You can see all the possible development for that card. If it's greed out meaning you never own it.

Or you can open menu swipe to the right and open collections. I find the above method easier for deciding which card to keep or discard.