Use the public-domain citation alone

Style note²Illinois courts21st and 22nd editions

A parallel citation is permitted but not required in an Illinois brief, and the reviewing courts give none in their own opinions.¹

1. 1Ill. S. Ct. R. 6; Ill. S. Ct. R. 341(g); Style Manual for the Supreme and Appellate Courts of Illinois pt. III (A)(2); B10.1.3 Court and Year of Decision. Tables: R. 10.3.1(a) Parallel citations in state court documents.
2. 2A style note: the rule in note 1 allows both forms and prefers one.