Effective January 1, 1980, the joint tax provided in Code Section 48-8-82 shall be levied in each special district in which prior to January 1, 1980, a joint county and municipal sales and use tax was levied pursuant to Ga. L. 1975, p. 984, Section 2 (as amended by Ga. L. 1975, Ex. Sess., p. 1729, Section 1; Ga. L. 1976, p. 1019, Sections 1-13; Ga. L. 1977, p. 1008, Section 1; Ga. L. 1978, p. 1429, Sections 1-3; Ga. L. 1978, p. 1460, Sections 1-3; Ga. L. 1978, p. 1678, Section 1; Ga. L. 1978, p. 1695, Section 1; Ga. L. 1979, p. 446, Section 1) or in which a referendum election had authorized the levying of such a tax within the special district.