Error in display Vietnamese word in title

Question

I got a problem with displaying my mother language in one title of my paper. Here is the code i use

\documentclass[12pt,a4paper]{amsart}


%% Packages that could be used

\usepackage{amscd,amssymb,amsthm}
\usepackage[utf8]{vietnam}
\usepackage{graphicx}
\usepackage{jipam}

\usepackage[utf8]{inputenc}
\usepackage[vietnam]{babel}


%\DeclareInputText


%% My definition
\newcommand{\mvec}[1]{\mbox{\bfseries\itshape #1}}


\title[Triangle inequality]{2 bất đẳng thức liên quan đến góc Brocard}
\author{Nguyen Duy Khanh}
\address{Hanoi, Vietnam}
\email{nguyenduykhanh@toanly.org}
\urladdr{http://www.toanly.org}

%\author{Author 2}
%\address{Line 3\\ Line 4\\ Address 2}
%\email{person2@inst.com}

%\keywords{Triangle,Inequality,Brocard angle}
%\subjclass[2000]{26D15}

\begin{document}

\begin{abstract}
Tiếng việt trong tiêu đề không hiển thị chính xác-The Vietnamese did not display correctly in the title.
\end{abstract}
\maketitle
\end{document}

The title should be 2 bất đẳng thức liên quan đến góc Brocard but it appeared as 2 BT NG THC LIN QUAN N GÂC BROCARD

My question is, what is the missing package that can help me to display the correct words? Please help me solve my problem. I really need it for writing my paper. Thank you very much!

Answer 1

There's a bad interaction when amsart tries to capitalize the title. Fixing it seems to be quite hard, I'm afraid. But you can resort to a trick: defining the capitalized title in a macro and using that one in \title

\documentclass[12pt,a4paper]{amsart}

\usepackage[utf8]{vietnam}

%% Packages that could be used
\usepackage{amscd,amssymb,amsthm}
\usepackage{graphicx}
%\usepackage{jipam}

%% My definition
\newcommand{\mvec}[1]{\mbox{\bfseries\itshape #1}}

\newcommand{\mytitle}{2 BẤT ĐẲNG THỨC LIÊN QUAN ĐẾN GÓC BROCARD}

\begin{document}

\title[Triangle inequality]{\mytitle}
\author{Nguyen Duy Khanh}
\address{Hanoi, Vietnam}
\email{nguyenduykhanh@toanly.org}
\urladdr{http://www.toanly.org}

%\author{Author 2}
%\address{Line 3\\ Line 4\\ Address 2}
%\email{person2@inst.com}

%\keywords{Triangle,Inequality,Brocard angle}
%\subjclass[2000]{26D15}

\begin{abstract}
Tiếng việt trong tiêu đề không hiển thị chính xác.
Now the Vietnamese is displayed correctly in the title.
\end{abstract}
\maketitle

\end{document}

Don't load both vietnam and babel.