Does the text contain a vague pronoun reference? At the conference, the authors met with some publishers to discuss their new books.

Yes.

Explanation: The text, "At the conference, the authors met with some publishers to discuss their new books", contains a vague pronoun reference because the pronoun "their" is a plural pronoun and the way the text is written, the pronoun "their" could refer to both nouns "authors" and "publishers". Since the pronoun "their" could refer to both "authors" and "publishers", then the text contains a vague pronoun reference as it is not clear whether the pronoun refers to "authors" or "publishers".