Approval voting is a single-winner voting system used for elections. Each voter may vote for (approve of) as many of the candidates as they wish. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote. Approval voting is a form of range voting with the range restricted to two values, 0 and 1. Approval voting can be compared to plurality voting without the rule that discards ballots which vote for more or less than one candidate. The system was described in 1976 by Guy Ottewell and also by Robert J. Weber, who coined the term "approval voting." It was more fully published in 1978 by political scientist Steven Brams and mathematician Peter Fishburn. Approval voting is used by some professional societies. Voting systems which incorporated aspects of approval voting have been used historically.