Italicize the word "in"

Style note²Federal courts, Illinois courts21st and 22nd editions

A shorter work inside a collection is introduced by an italicized “in”, which marks where the work's own title ends and the volume's begins.¹

1. 1R. 15.5.1(a) Works by various authors; R. 15.5.1 Works in Collection Generally.
2. 2A style note: the rule in note 1 allows both forms and prefers one.