possible reference to more than one word

In the original sentence, they could refer to the signals or to the airwaves.

reference implied but not stated

What does which refer to? The editing clarifies what employees resented.

A pronoun should refer clearly to the word or words it replaces (called the antecedent) elsewhere in the sentence or in a previous sentence. If more than one word could be the antecedent, or if no specific antecedent is present, edit to make the meaning clear. (See Chapter 27.)