How to reference different sources in a list?
I think the method you've proposed, while cumbersome and intrusive, is also the correct way to do things, as you will be assigning a specific item to a specific source. That is the point of citing original source material in the first place. So while it may be somewhat unsightly (particularly if using a Harvard-like style in which the authors are listed as part of the reference), what you're doing has the advantage of being unambiguous and completely legitimate.