  Re (1): The fact that M1 can be expanded to a Tarskian model is not surprising, given the reasoning in Example 1.1, above: any initial hypothesis about the truth values of the three sentences in question leads, after three iterations of the revision process, to a stable hypothesis that (Tβ   ∨  Tγ) and Tα are true, while ¬Tα is false. The fact that M1 can be expanded to exactly one Tarskian model needs the so-called Transfer Theorem, Gupta and Belnap 1993, Theorem 2D.4. 