Use the gazette form for the year cited

Error²Federal courts, Illinois courts21st and 22nd editions

The Swiss federal legislative gazette was bound in volumes through 1997 and paginated by year from 1998 on, so the year of the issue decides whether a volume belongs between the gazette's abbreviation and the page.¹

1. 1T2.43 Switzerland; T2.41 Switzerland. Tables: T10.2 Australian Cities and States; Canadian Cities, Provinces, and Territories; and U.K. Cities and Constituent Countries,; T10.3 Countries and Regions.
2. 2An error: the rule in note 1 allows one form, and this is not it.