Definition:Gentzen Proof System/Instance 1/Alpha-Rule/Notation

Definition
Let $\mathscr G$ be instance 1 of a Gentzen proof system.

Let $\mathbf A$ be an $\alpha$-formula, with $\mathbf A_1, \mathbf A_2$ as in the table of $\alpha$-formulas.

In a tableau proof, the $\alpha$-rule can be used as follows: