§ 110. Income debentures. With the approval of the supervising agency, the certificate creating a redevelopment company, or an amended certificate, may authorize the issuance of income debenture certificates bearing no greater interest than six per centum per annum. Such income debenture certificates and any instrument under which they are issued may contain such other provisions, including provision for amortization by serial maturities, through the operation of a sinking fund or otherwise, as may be approved by the supervising agency.