What singer has won the Eurovision Song Contest twice?

Explanation

Johnny Logan won the ESC for Ireland in 1980 with "What's Another Year" and in 1987 with "Hold Me Now" as the only performer to win twice. There are several song writers, however, who have won twice - for instance Willy van Hemert (the Netherlands, 1957, 1959), Yves Dessca (Monaco 1971, Luxembourg 1972). What makes Logan unique is that he has been behind three winning entries, either as a performer or as a song writer.