Non-terminal symbol `Vars`

Defining rules for nonterminal symbol Vars:

`Vars`		`Var`
		`Vars` `Var`

Occurrences of symbol Vars in body of other rules:

`Vars_opt`		`Vars`
`Formula`		`EXISTS` `Vars` `OPENPAR` `Formula` `CLOSEPAR`

Non-terminal symbol Vars