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I am reading the paper Double fibrations. Throughout the paper, they make use of a (2-)category , however I cannot seem to find where it is defined. I could certainly guess what it, based on the generalised version in Definition 3.24. Is this standard notation?
My assumption is that the objects are pseudo-functors from a category , i.e. an [[indexed category]].
Yes, I think that's what they mean.
I wouldn't say it's standard notation.