Analysis of information sources in references of the Wikipedia article "Zwolle" in English language version.
De stedelijke geldmiddelen, het nationaal inkomen zouden wij nu zeggen, die in 1402 nog 6.000 gulden bedroegen waren in 1450 bijna verzesvoudigd tot 34.000 gulden. (Translated: The city's financial resources, the national income as we would now call it, which were 6,000 guilders in 1402, had by 1450 multiplied by six to 34,000 guilders.)
De stedelijke geldmiddelen, het nationaal inkomen zouden wij nu zeggen, die in 1402 nog 6.000 gulden bedroegen waren in 1450 bijna verzesvoudigd tot 34.000 gulden. (Translated: The city's financial resources, the national income as we would now call it, which were 6,000 guilders in 1402, had by 1450 multiplied by six to 34,000 guilders.)