| | | Date | Location | | 1951 | Paris | | 1953 | Milan | | 1955 | The Hague | | 1957 | Zurich | | 1959 | Wiesbaden | | 1962 | Copenhagen | | 1965 | London | | 1968 | Brussels | | 1971 | Stockholm | | 1973 | Washington | | 1975 | Barcelona |
| | Date | Location | | 1981 | Helsinki | | 1983 | Paris | | 1985 | Oslo | | 1987 | Warsaw | | 1989 | Tianjin | | 1991 | Florence | | 1993 | London | | 1995 | Interlaken | | 1998 | Copenhagen | | 2001 | Hamburg | | 2004 | Kyoto |
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