If the series is long and complex or any one element has a comma within it, separate each element of the series with a semicolon:
The company has offices in Greensboro, North Carolina; Atlanta, Georgia; Los Angeles, California; and Taipei, Taiwan. (Commas within elements.)
The committee reviewed the Jones Report, which was written in 2006; the Jackson Study, which came from the regional office; and the Commissioner's Report, which prompted the initial controversy. (Commas within elements.)
"Since the earliest days philosophers have dreamed of a country where the mind and spirit of man would be free; where there would be no limits to inquiry; where men would be free to explore the unknown and to challenge the most deeply rooted beliefs and principles." Justice Hugo Black, The Bill of Rights, 35 N.Y.U. L. Rev. pp. 880-81 (1960).
(Elements are long and complex.)