We ordered this in addition to the jumbo pellets! This guide is very informative and helpful to have while dissecting (yes, it's a little on the pricey side, but it's well worth it!)
Advanced Owl Pellet Guide
Although this guide is a little on the pricey side, I feel that it is well worth the cost. It contains a lot of clear information on owls with sharp black and white photographs, a vole skeleton with the bones identified, and a key to skulls found in pellets. The guide and pellets ordered from Home Science Tools makes a good stand alone lesson. All ages will enjoy this. Recommended.