Interim certificate. Authorized, §50-9-36. Investments. Authorized investments, §50-9-45. Issuance. Authorized, §50-9-30. Combination of projects. Issuance authorized, §50-9-38. Form, §50-9-31. Refunding bonds, §50-9-44. 922 INDEX GEORGIA BUILDING AUTHORITY —Cont’d Revenue bonds —Cont’d Judgments. Validation of bonds. Finality and conclusiveness of judgments, §50-9-46. Lost bonds. Replacement, §50-9-37. Mutilated bonds. Replacement, §50-9-37. Negotiable instruments, §50-9-33. Payment. Enforcement. Rights and remedies of bondholders, §50-9-43. Place, §50-9-31. Sinking fund, §50-9-42. Source, §50-9-30. Trust indentures as security, §50-9-40. Pledge of credit of state.