\documentclass[12pt,a0paper]{article}
\bibliographystyle{unsrt}
\usepackage{amssymb,amsmath}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{latexsym}
%\usepackage{bbold}
\usepackage{hyperref}
\usepackage{graphicx}
\usepackage{multirow}
\textwidth16.5cm
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\begin{document}
\begin{center}
{
	\includegraphics[scale=0.16]{pid_0p07_1geo-1_0p116.png}
	\includegraphics[scale=0.16]{pid_0p07_1geo0p116_0p44.png}
	\includegraphics[scale=0.16]{pid_0p07_1geo0p44_0p616.png}
	\includegraphics[scale=0.16]{pid_0p07_1geo0p616_1.png}
}
{
	\includegraphics[scale=0.16]{pid_0p03_0p07geo-1_0p116.png}
	\includegraphics[scale=0.16]{pid_0p03_0p07geo0p116_0p44.png}
	\includegraphics[scale=0.16]{pid_0p03_0p07geo0p44_0p616.png}
	\includegraphics[scale=0.16]{pid_0p03_0p07geo0p616_1.png}
}
{
	\includegraphics[scale=0.16]{pid_-0p005_0p03geo-1_0p116.png}
	\includegraphics[scale=0.16]{pid_-0p005_0p03geo0p116_0p44.png}
	\includegraphics[scale=0.16]{pid_-0p005_0p03geo0p44_0p616.png}
	\includegraphics[scale=0.16]{pid_-0p005_0p03geo0p616_1.png}
}
{
	\includegraphics[scale=0.16]{pid_-0p03_-0p005geo-1_0p116.png}
	\includegraphics[scale=0.16]{pid_-0p03_-0p005geo0p116_0p44.png}
	\includegraphics[scale=0.16]{pid_-0p03_-0p005geo0p44_0p616.png}
	\includegraphics[scale=0.16]{pid_-0p03_-0p005geo0p616_1.png}
}
\end{center}
\end{document}
