A quick search gives at least the following 8 - the site is in Russian and a pirate site, so I can't post a link or give names, only numbers:
5/1971
N1/1972
3/1974
2/1975
N1/1975
7/1977 (This is the square in Gdansk - I won this in the recent MM contest)
12/1978
8-9/1979
__________________
-Dan
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