Basic Modern Algebraic Geometry
... a tuple of objects (A1 , A2 , . . . , An ) from categories Ci , i = 1, 2, . . . , n assigns
an object T (A1 , A2 , . . . , An ) if a category D, and which is covariant in some of
the variables, contravariant in othes, and such that the obvious generalization
of the naturallity condition holds. In pa ...