The proceeds of any notes or certificates of indebtedness issued under the provisions of this article shall be placed in a special fund and shall be expended only for the purpose or purposes for which they were issued as shown by the resolution authorizing the issuance thereof. If a balance shall remain of the proceeds of such notes or certificates of indebtedness after the purpose or purposes for which they were issued shall have been accomplished, such balance shall be used to pay such obligations at or before maturity and may be transferred to any sinking fund previously established for the payment thereof.
Proceeds from the sale of notes or certificates of indebtedness not immediately necessary for expenditure shall be invested in the same manner as surplus funds of the governing authority may be invested.