All bonds issued under this law, except as otherwise provided in § 4644 of this title and except bonds of authorized issues of $30,000 or less and having a maximum maturity of not more than 5 years from the date of issuance of such bonds, shall be sold at public sale upon sealed proposals after at least 10 days notice published at least once in a publication carrying municipal bond notices and devoted primarily to financial news or to the subject of state and municipal bonds, published in the City of New York, and at least 10 days notice published at least once in a newspaper published in the County and having general circulation therein. Bonds of authorized issues of $30,000 or less, and maturing as hereinabove set forth, and all bond anticipation notes may be sold at private sale by such financial officer as the county government may by resolution provide.