== Validade global de sequentes ==
=== <math> \exists x \forall y. \varphi </math> ▷ <math> \forall y \exists x. \varphi </math> ===
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=== <math> \forall y \exists x. \varphi </math> ▶ <math> \exists x \forall y. \varphi </math> ===
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