Abbreviate the periodical's name

Error²Federal courts, Illinois courts21st and 22nd editions

An English periodical title is abbreviated from the periodical tables — T13 for institutional names, T6 and T10 for single words — and a word none of them lists stays spelled out.¹

1. 1R. 16.4 Consecutively Paginated Journals; R. 16.5 Nonconsecutively Paginated Journals and Magazines; R. 6.1(a) Spacing; B16.1.1 Consecutively Paginated Journals; B16.1.2 Nonconsecutively Paginated Journals and Magazines; B16.1.4 Newspaper Articles; R. 16.1 Basic Citation Forms; R. 16.7.7 Proceedings, Regular Publications by Institutes, and ABA Section Reports; R. 16.7.8 Newsletters and Other Noncommercially Distributed Periodicals. Tables: T13 Institutional Names in Periodical Titles; T6 Case Names and Institutional Authors in Citations.
2. 2An error: the rule in note 1 allows one form, and this is not it.