Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
SERIES CONSTRUCTIONS
list three or more words, phrases, or clauses of roughly equal weight in syntax. In speech, intonation, and in writing, punctuation (usually a comma) links the several items in the series: They issued us our eating utensils: a tin cup, a mess kit, a spoon, a knife, a fork, and a canteen. Conventionally, the last two items in the series are linked with a coordinating conjunction, usually (but not always) preceded by a comma in written American English. Some American and most British stylebooks permit omission of this comma when the conjunction is there, but it is easier to include both every time.
