Shorten the name to the surname

Warning²Federal courts, Illinois courts21st and 22nd editions

A “supra” short form is built from the author's surname alone — “Posner, supra, at 205” — with the full name kept for an institutional author.¹

1. 1R. 4.2(a) “Supra.”; B15.2 Short Form Citation.
2. 2A warning: the form is usually wrong under the rule in note 1, and context can justify it.