\documentclass[12pt]{article} \usepackage{kpfonts} \usepackage[utf8]{vietnam} \usepackage{amsmath,amsxtra,amssymb,latexsym,amscd,amsthm} %\usepackage[light]{kpfonts} \usepackage[a4paper,left=1.5cm,right=1.5cm,top=1cm,bottom=1.5cm]{geometry} \renewcommand{\baselinestretch}{1.2} \begin{document} $\widearcarrow{ABC}$\\ \end{document}