What type of details about jef scherens can be gathered from the following bio? Bio: joseph '' jef '' scherens -lrb- 17 february 1909 -- 9 august 1986 -rrb- was a belgian professional track cyclist , specialising in sprint where he won seven world championships . scherens was born in werchter and died in leuven . the grote prijs jef scherens , which is held in leuven , is named in his honour .
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