75 ILCS 5/4-8

In cities of more than 500,000 population, the board of trustees shall be governed by the provisions of Division 10 of Article 8 of the Illinois Municipal Code, as heretofore and hereafter amended, in relation to the letting of contracts and purchase orders in behalf of any library and the power, functions and authority of the purchasing agent, board of standardization and corporate authority in such cities.