Where do the references come from?

[slvcsl]

Hi, great work!
I was wondering where the references used in the evaluation come from.
The paper references "Evaluating the Factual Consistency of Abstractive Text Summarization," but I do not seem to be able to find details in the paper. Specifically, I would be interested in knowing whether the references are human written (and, in that case, whether guidelines are available) or whether they are obtained through some semi automatic process.