don't put anything IMO
about as useful as writing curriculum vitae at the top in a large font - tis just a waste of space
If they want a personal reference, they'll ask for one, if they want to contact former employers - you've got them listed on the CV anyway
lots of places outsource background checking too these days - you could be given a form and be asked to list all employers for up to the past 10 years + account for any gaps of greater than 1 month - someone at the background checking place will then check each of these