 Note that Approval Voting satisfies Neutrality even though it is not listed as one of the characterizing properties in the above theorem. This is because Alos-Ferrer (2006) showed that Neutrality is a consequence of Faithfulness, Cancellation and Reinforcement. See Fishburn 1978a and Baigent and Xu 1991 for alternative characterizations of Approval Voting, and Xu 2010 for a survey of the characterizations of Approval Voting (cf. the characterization of Approval Voting from Goodin and List 2006). 