Not less than three copies of each primary code adopted by reference, and of each secondary code pertaining thereto, all certified to be true copies by the county executive officer and the county clerk, shall be filed in the office of the county clerk at least fifteen days preceding the hearing and shall be kept there for public inspection while the ordinance is in force. After the adoption of the code by reference, one of the copies of the primary code and of each secondary code may be kept in the office of the chief enforcement officer instead of in the office of the county clerk. Following the adoption of any code, the county clerk shall at all times maintain a reasonable supply of copies of the primary code and of any secondary codes incorporated in it by reference, available for purchase by the public at a moderate price.