I'm sort of baffled, myself. I see no reason why this would be unfilterable. I'm marking this as an unanswered question, hopefully someone comes to our rescue here.
Measuring and Increasing the ROI of Your Content Resources
4/22/2013 Do you want to know the value of your content? In today's post, Mike Pantoliano shares his tips for calculating the real ROI of your content strategy and marketing efforts.