src/Doc/Implementation/document/root.tex

 \documentclass[12pt,a4paper,fleqn]{report}
 \usepackage[T1]{fontenc}
-\usepackage{latexsym,graphicx}
+\usepackage{graphicx}
 \usepackage[refpage]{nomencl}
 \usepackage{iman,extra,isar,proof}
 \usepackage[nohyphen,strings]{underscore}
 \usepackage{isabelle}
 \usepackage{isabellesym}