  We use fibrations of complete Segal spaces to construct four complete Segal
spaces: Reedy fibrant simplicial spaces, Segal spaces, complete Segal spaces,
and spaces. Moreover, we show each one comes with a universal fibration that
classifies Reedy left fibrations, Segal coCartesian fibrations, coCartesian
fibrations and left fibrations and prove these are representable fibrations.
Finally, we use equivalences between quasi-categories and complete Segal spaces
to present analogous constructions using fibrations of quasi-categories.
