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\usepackage{amsmath,amsfonts,amssymb,amsthm,caption}
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\begin{document}
\newpage 
 \clearpage 
 \begin{table}[!h] \footnotesize 
\addtocounter{table}{0} 
\caption{\textbf{Table title}} 
\par {Table description} 

 \vspace{2mm} 

 \begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l*{4}{c}} 
 \hline \noalign{\smallskip} 
\multicolumn{5}{@{} l}{Panel A: Some title} \\ 
 \hline \noalign{\smallskip} 
& \multicolumn{2}{c}{Group1}  \\ 
\cline{2-3}  
 & Model 1 & Model 2 & Model 3 & Model 4 \\ 
 \hline \noalign{\smallskip} 
cons & 0.51*** & 0.70*** & 0.51*** & 0.73*** \\ 
 & (3.91) & (21.48) & (3.91) & (167.36) \\ 
x & 0.35 & 0.57** & 0.35 & 0.64* \\ 
 & (1.29) & (2.85) & (1.29) & (2.26) \\ 
z &  & -0.64** &  & -0.77** \\ 
 &  & (-3.55) &  & (-2.91) \\ 
$R^2$ & 0.19 & 0.49 & 0.19 & 0.35 \\ 
Observations & 9 & 9 & 9 & 9 \\ 
 \hline \noalign{\smallskip} 
\end{tabular*}
 \smallskip 
\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l*{4}{c}} 
\multicolumn{5}{@{} l}{Panel B: Some title} \\ 
 \hline \noalign{\smallskip} 
& \multicolumn{2}{c}{Group1}  \\ 
\cline{2-3}  
 & Model 1 & Model 2 & Model 3 & Model 4 \\ 
 \hline \noalign{\smallskip} 
cons & 0.51*** & 0.70*** & 0.51*** & 0.73*** \\ 
 & (3.91) & (21.48) & (3.91) & (167.36) \\ 
x & 0.35 & 0.57** & 0.35 & 0.64* \\ 
 & (1.29) & (2.85) & (1.29) & (2.26) \\ 
z &  & -0.64** &  & -0.77** \\ 
 &  & (-3.55) &  & (-2.91) \\ 
$R^2$ & 0.19 & 0.49 & 0.19 & 0.35 \\ 
Observations & 9 & 9 & 9 & 9 \\ 
 \hline \noalign{\smallskip} 
\end{tabular*} 
\label{} 
 \end{table} 
 
 \newpage 
 \clearpage 
 \begin{table}[!h] \footnotesize 
\addtocounter{table}{0} 
\caption{\textbf{Table title}} 
\par {Table description} 

 \vspace{2mm} 

 \begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l*{4}{c}} 
 \hline \noalign{\smallskip} 
\multicolumn{5}{@{} l}{Panel A: Some title} \\ 
 \hline \noalign{\smallskip} 
& \multicolumn{2}{c}{Group1}  \\ 
\cline{2-3}  
 & Model 1 & Model 2 & Model 3 & Model 4 \\ 
 \hline \noalign{\smallskip} 
cons & 0.51*** & 0.70*** & 0.51*** & 0.73*** \\ 
 & (3.91) & (21.48) & (3.91) & (167.36) \\ 
x & 0.35 & 0.57** & 0.35 & 0.64* \\ 
 & (1.29) & (2.85) & (1.29) & (2.26) \\ 
z &  & -0.64** &  & -0.77** \\ 
 &  & (-3.55) &  & (-2.91) \\ 
$R^2$ & 0.19 & 0.49 & 0.19 & 0.35 \\ 
Observations & 9 & 9 & 9 & 9 \\ 
 \hline \noalign{\smallskip} 
\end{tabular*}
 \smallskip 
\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l*{4}{c}} 
\multicolumn{5}{@{} l}{Panel B: Some title} \\ 
 \hline \noalign{\smallskip} 
& \multicolumn{2}{c}{Group1}  \\ 
\cline{2-3}  
 & Model 1 & Model 2 & Model 3 & Model 4 \\ 
 \hline \noalign{\smallskip} 
cons & 0.51*** & 0.70*** & 0.51*** & 0.73*** \\ 
 & (3.91) & (21.48) & (3.91) & (167.36) \\ 
x & 0.35 & 0.57** & 0.35 & 0.64* \\ 
 & (1.29) & (2.85) & (1.29) & (2.26) \\ 
z &  & -0.64** &  & -0.77** \\ 
 &  & (-3.55) &  & (-2.91) \\ 
$R^2$ & 0.19 & 0.49 & 0.19 & 0.35 \\ 
Observations & 9 & 9 & 9 & 9 \\ 
 \hline \noalign{\smallskip} 
\end{tabular*} 
\label{} 
 \end{table} 

\end{document}