How to count without including duplicates?

kelih

I want to count a list of names without including duplicates. This is a list of all publications our group had last year. Some people had more than 1 publication, but I want to know how many total faculty of each appointment type had publications. I want to first filter by column A (journal vs poster publication), then column B (appointment type - faculty vs staff), then count column C (names) without including duplicates. 

Paul Newcome

Will this be on the same sheet or on a separate sheet?