Complex sentence: Most notable among Duncan's invention credits is the concept of the premium incentive--a marketing tactic wherein one collects proofs of purchase ("i.e." boxtops or UPC barcodes) and redeems them for rewards, such as small toys or discount coupons.
Split into simpler sentences: Most notable among Duncan's invention credits is the concept of the' premium incentive'. This is a marketing tactic: one collects proofs of purchase (i.e. boxtops or UPC barcodes) and redeems them for rewards, such as small toys or discount coupons.