Should the verb, in the following sentence, be singular or plural?
A series of samples was produced.
In a related question I found a reference. However the text in that reference seems to contradict itself.
Nouns that are “collective” take a singular verb when the group as a whole is meant.
Commonly used collective nouns include “number,” “majority,” “series,” and “variety.”
Note that when collective nouns refer to a singular group as a whole they are often preceded by the word “a”;
Based on these rules, I would expect that, since I am using an indefinite article a series, the singular form of the verb is to be used. However the reference uses plural in an example
A series of western blots were performed to assay protein expression.