Use the citation number form

Error²Federal courts, Illinois courts21st and 22nd editions

In a citation, second and third are written “2d” and “3d” rather than “2nd” and “3rd”, and an edition designation inside the publication parenthetical follows that form.¹

1. 1R. 15.4(a)(ii) Multiple editions by the same publisher; R. 6.2(b)(ii) Ordinals; R. 15.4 Edition, Publisher, and Date.
2. 2An error: the rule in note 1 allows one form, and this is not it.