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At the Tokyo Olympics two years later she finished second in both events.
At the Tokyo Olympics two years later she finished second in both events.
Her international career started in 1962 when, at the age of fifteen, she took the European title in the 100 m butterfly in Leipzig. She was also part of the silver 4×100 m medley relay team Kok reached her peak at the 1968 Summer Olympics in Mexico City.
The 100 meter butterfly race in that Olympic Games ended in disappointment for her, when she did not feel well beforehand, and finished in fourth place.
In her memoirs written by Henk Lichtenveldt, she stated:.
She was also good at freestyle swimming, which showed when she took second place in the 400 metres at the 1966 European Championships in Utrecht.