  Kamp's theorem established the expressive equivalence of the temporal logic
with Until and Since and the First-Order Monadic Logic of Order (FOMLO) over
the Dedekind-complete time flows. However, this temporal logic is not
expressively complete for FOMLO over the rationals. Stavi introduced two
additional modalities and proved that the temporal logic with Until, Since and
Stavi's modalities is expressively equivalent to FOMLO over all linear orders.
We present a simple proof of Stavi's theorem.
