Programs or projects to which this subpart applies must maintain copies of the certifications and documentation specified in Sec. Sec. 50.304 and 50.306 for three years pursuant to the retention and custodial requirements for records at 45 CFR 74.20 et seq. [43 FR 4570, Feb. 2, 1978, as amended at 44 FR 61598, Oct. 26, 1979]