Use "&" between the two authors

Warning²Federal courts, Illinois courts22nd edition only

An archived document's author is written like any other author, joined by an ampersand rather than the word “and”. Only a personal-name author run beside an archival “on file with” note is checked.¹

1. 1R. 23.2(a) In general; R. 15.1(a) Two or three authors. Tables: T6 Case Names and Institutional Authors in Citations.
2. 2A warning: the form is usually wrong under the rule in note 1, and context can justify it.