Import of AFP for Isabelle 2021.

UPF_Firewall/document/root.tex

@@ -16,7 +16,7 @@
 \usepackage{paralist}
 \usepackage{xspace}
 \usepackage{amsmath}
-\usepackage[USenglish]{babel}
+\usepackage[english]{babel}
 \newcommand{\testgen}{HOL-TestGen\xspace}
 \newcommand{\testgenFW}{HOL-TestGen/FW\xspace}
 \usepackage[numbers, sort&compress, sectionbib]{natbib}