"Opinions vary among writers and editors on the usage or avoidance of the serial comma. In American English, the serial comma is standard usage in non-journalistic writing that follows the Chicago Manual of Style. Journalists, however, usually follow the AP Stylebook, which advises against it."
"Opinions vary among writers and editors on the usage or avoidance of the serial comma. In American English, the serial comma is standard usage in non-journalistic writing that follows the Chicago Manual of Style. Journalists, however, usually follow the AP Stylebook, which advises against it."
http://en.wikipedia.org/wiki/Serial_comma