
    \begin{tabular}{ccc}
    \begin{tikzpicture}[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center}]
    %K33
    \coordinate (h1) at ($(3,2,1)+(2,3,1)$);
    \coordinate (h2) at ($(2,3,1)+(1,3,2)$);
    \coordinate (h3) at ($(1,3,2)+(1,2,3)$);
    \coordinate (h4) at ($(1,2,3)+(2,1,3)$);
    \coordinate (h5) at ($(2,1,3)+(3,1,2)$);
    \coordinate (h6) at ($(3,1,2)+(3,2,1)$);
    \draw[draw=white, fill=black!10] (h1) -- (h2) -- (h3) -- (h4) -- (h5) -- (h6) -- cycle;
    \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;
    \node (123) at (1,2,3) {};    
    \node (132) at (1,3,2) {};    
    \node (213) at (2,1,3) {};    
    \node (231) at (2,3,1) {};    
    \node (312) at (3,1,2) {};    
    \node (321) at (3,2,1) {};    
    \draw[blue] (123) -- (132) -- (231) -- (321) -- (312) -- (213) -- (123); 
    \draw[blue] (123) -- (0.5,2,3.5);
    \draw[blue] (132) -- (0.5,3.5,2);
    \draw[blue] (213) -- (2,0.5,3.5);
    \draw[blue] (231) -- (2,3.5,0.5);
    \draw[blue] (321) -- (3.5,2,0.5);
    \draw[blue] (312) -- (3.5,0.5,2);
    \draw[->, orange, ultra thick] (h2) -- (h1);
    \draw[->, skyblue, ultra thick] (h2) -- (h3);
    \draw[->, bluishgreen, ultra thick] (h4) -- (h3);
    \draw[->, orange, ultra thick] (h4) -- (h5);
    \draw[->, skyblue, ultra thick] (h6) -- (h5);
    \draw[->, bluishgreen, ultra thick] (h6) -- (h1);
    \end{tikzpicture}
    &\begin{tikzpicture}%
            	[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},
                scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center},
                boundary style one/.style={->, orange, ultra thick},
                boundary style two/.style={->, bluishgreen, ultra thick},
                boundary style three/.style={->, skyblue, ultra thick},
                ]
        
            % Modify these parameters to determine the size of the graph:
            \def\kone{1}
            \def\ktwo{1}
            \def\kthree{1}



            % Shaded hexagon
            \coordinate (h1) at ($(3,2,1)+\kone*(3,0,0)$);
            \coordinate (h3) at ($(1,3,2)+\ktwo*(0,3,0)$);
            \coordinate (h5) at ($(2,1,3)+\kthree*(0,0,3)$);
            \coordinate (h2) at ($(h1)+(h3)$);
            \coordinate (h4) at ($(h3)+(h5)$);
            \coordinate (h6) at ($(h5)+(h1)$);
            
            \draw[draw=white, fill=black!10] (h1) -- (h2) -- (h3) -- (h4) -- (h5) -- (h6) -- cycle;

            % Central hexagon
            \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;

            % FUNDAMENTAL TILE:
            \foreach \a in {0,...,\kone}{
                \foreach \b in {0,...,\ktwo}{
                    \foreach \c in {0,...,\kthree}{
                        \begin{scope}[shift={($\a*(3,0,0)+\b*(0,3,0)+\c*(0,0,3)$)}]
                            \node (\a\b\c 123) at (1,2,3) {};
                            \node (\a\b\c 213) at (2,1,3) {};
                            \node (\a\b\c 132) at (1,3,2) {};
                            \node (\a\b\c 231) at (2,3,1) {};
                            \node (\a\b\c 312) at (3,1,2) {};
                            \node (\a\b\c 321) at (3,2,1) {};
                        
                            % \draw[blue] (123) -- (213) -- (312) -- (321) -- (231) -- (132) -- (123);      
                            \draw[blue] (\a\b\c 213) -- (\a\b\c 123) -- (\a\b\c 132) -- (\a\b\c 231);      
                        \end{scope}
                    }
                }    
            }    
        
        
            %BOUNDARY: 
            %Boundary edges one
            \begin{scope}[shift={($\kthree*(0,0,3)$)}]
            \draw[boundary style one] (2,1,3) -- (3,1,2);
            \foreach \i in {1,...,\kone}{
                \begin{scope}[shift={($\i*(3,0,0)$)}]
                        \draw[boundary style one] (1,2,3) -- (2,1,3) -- (3,1,2);
                \end{scope}
                }        
            \end{scope}
            %
            \begin{scope}[shift={(${\ktwo+1}*(0,3,0)$)}]
            \draw[boundary style one] (2,1,3) -- (3,1,2);
            \foreach \i in {1,...,\kone}{
                \begin{scope}[shift={($\i*(3,0,0)$)}]
                        \draw[boundary style one] (1,2,3) -- (2,1,3) -- (3,1,2);
                \end{scope}
                }        
            \end{scope}
            %%%
        
            %Boundary edges two
            \begin{scope}[shift={($\kone*(3,0,0)$)}]
            \draw[boundary style two] (3,2,1) -- (2,3,1);
            \foreach \i in {1,...,\ktwo}{
                \begin{scope}[shift={($\i*(0,3,0)$)}]
                        \draw[boundary style two] (3,1,2) -- (3,2,1) -- (2,3,1);
                \end{scope}
                }        
            \end{scope}
            %
            \begin{scope}[shift={(${\kthree+1}*(0,0,3)$)}]
            \draw[boundary style two] (3,2,1) -- (2,3,1);
            \foreach \i in {1,...,\ktwo}{
                \begin{scope}[shift={($\i*(0,3,0)$)}]
                        \draw[boundary style two] (3,1,2) -- (3,2,1) -- (2,3,1);
                \end{scope}
                }        
            \end{scope}
            %%%
        
            %Boundary edges three
            \begin{scope}[shift={($\ktwo*(0,3,0)$)}]
            \draw[boundary style three] (1,3,2) -- (1,2,3);
            \foreach \i in {1,...,\kthree}{
                \begin{scope}[shift={($\i*(0,0,3)$)}]
                        \draw[boundary style three] (2,3,1) -- (1,3,2) -- (1,2,3);
                \end{scope}
                }        
            \end{scope}
            %
            \begin{scope}[shift={(${\kone+1}*(3,0,0)$)}]
            \draw[boundary style three] (1,3,2) -- (1,2,3);
            \foreach \i in {1,...,\kthree}{
                \begin{scope}[shift={($\i*(0,0,3)$)}]
                        \draw[boundary style three] (2,3,1) -- (1,3,2) -- (1,2,3);
                \end{scope}
                }        
            \end{scope}
            %%%

        \end{tikzpicture}
    &
    \begin{tikzpicture}[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center}]
    %MobiusKantor
    \coordinate (h1) at ($3*(3,1,2)$);
    \coordinate (h2) at ($3*(1,3,2)$);
    \coordinate (h3) at ($2*(1,2,3)+2*(2,1,3)$);
    \coordinate (h4) at ($2*(3,2,1)+2*(2,3,1)$);
    \draw[draw=white, fill=black!10] (h1) -- (h3) -- (h2) -- (h4) --  cycle;
    \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;
    \node (123) at (1,2,3) {};    
    \node (132) at (1,3,2) {};    
    \node (213) at (2,1,3) {};    
    \node (231) at (2,3,1) {};    
    \node (312) at (3,1,2) {};    
    \node (321) at (3,2,1) {};    
    \node (024) at (0,2,4) {};    
    \node (042) at (0,4,2) {};    
    \node (204) at (2,0,4) {};    
    \node (240) at (2,4,0) {};    
    \node (402) at (4,0,2) {};    
    \node (420) at (4,2,0) {};   
    \node (015) at (0,1,5) {};    
    \node (051) at (0,5,1) {};    
    \node (105) at (1,0,5) {};    
    \node (150) at (1,5,0) {};    
    \node (501) at (5,0,1) {};    
    \node (510) at (5,1,0) {};  
    \node (-134) at (-1,3,4) {};    
    \node (-143) at (-1,4,3) {};    
    \node (3-14) at (3,-1,4) {};    
    \node (34-1) at (3,4,-1) {};    
    \node (4-13) at (4,-1,3) {};    
    \node (43-1) at (4,3,-1) {};  
    \draw[blue] (123) -- (132) -- (231) -- (321) -- (312) -- (213) -- (123) -- (024) -- (015) -- (105) -- (204) -- (213);
    \draw[blue] (321) -- (420) -- (510) -- (501) -- (402) -- (312);
    \draw[blue] (132) -- (042) -- (051) -- (150) -- (240) -- (231);
    \draw[blue] (402) -- (4-13) -- (3-14) -- (204);
    \draw[blue] (024) -- (-134) -- (-143) -- (042);
    \draw[blue] (240) -- (34-1) -- (43-1) -- (420);
    \draw[->, bluishgreen, ultra thick] (-143) -- (-134) -- (024); 
    \draw[bluishgreen, ultra thick] (024) -- (015);
    \draw[->,bluishgreen, ultra thick] (43-1) -- (420) -- (510);
    \draw[bluishgreen, ultra thick] (510) -- (501);
    \draw[->,orange, ultra thick] (4-13) -- (3-14) -- (204);
    \draw[orange, ultra thick] (204) -- (105);
    \draw[->,orange, ultra thick] (34-1) -- (240) -- (150);
    \draw[orange, ultra thick] (150)-- (051);
    \node (-161) at (-1,6,1) {};    
    \node (6-11) at (6,-1,1) {};     
    \node (-253) at (-2,5,3) {};    
    \node (5-23) at (5,-2,3) {};    
    \node (-262) at (-2,6,2) {};      
    \node (6-22) at (6,-2,2) {};   
    \draw[blue, dashed] (501) -- (6-11) -- (6-22);
    \draw[blue, dashed] (4-13) -- (5-23) -- (6-22);
    \draw[blue, dashed] (051) -- (-161) -- (-262);
    \draw[blue, dashed] (-143) -- (-253) -- (-262);
    \end{tikzpicture}
    \\
    \(K_{3,3}\) & Heawood & M\"obius-Kantor
    \\
$\begin{pmatrix}
    1  & -1 & \\ 
       & 1 & -1  \\
    -1  &   & 1  \\
\end{pmatrix}$&
$\begin{pmatrix}
    2  & -1 & \\ 
       &  2 & -1  \\
    -1 &    & 2   \\
\end{pmatrix}$& 
$\begin{pmatrix}
    2  &    & -1 \\ 
       &  2 & -1 \\
    -1 & -1 &  3 \\
\end{pmatrix}$    \\
    \begin{tikzpicture}[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center}]
    %Pappus
    \coordinate (h1) at ($3*(3,2,1)$);
    \coordinate (h2) at ($3*(2,3,1)$);
    \coordinate (h3) at ($3*(1,3,2)$);
    \coordinate (h4) at ($3*(1,2,3)$);
    \coordinate (h5) at ($3*(2,1,3)$);
    \coordinate (h6) at ($3*(3,1,2)$);
    \draw[draw=white, fill=black!10] (h1) -- (h2) -- (h3) -- (h4) -- (h5) -- (h6) -- cycle;
    \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;
    \node (123) at (1,2,3) {};    
    \node (132) at (1,3,2) {};    
    \node (213) at (2,1,3) {};    
    \node (231) at (2,3,1) {};    
    \node (312) at (3,1,2) {};    
    \node (321) at (3,2,1) {};    
    \node (024) at (0,2,4) {};    
    \node (042) at (0,4,2) {};    
    \node (204) at (2,0,4) {};    
    \node (240) at (2,4,0) {};    
    \node (402) at (4,0,2) {};    
    \node (420) at (4,2,0) {};   
    \node (015) at (0,1,5) {};    
    \node (051) at (0,5,1) {};    
    \node (105) at (1,0,5) {};    
    \node (150) at (1,5,0) {};    
    \node (501) at (5,0,1) {};    
    \node (510) at (5,1,0) {};  
    \node (-134) at (-1,3,4) {};    
    \node (-143) at (-1,4,3) {};    
    \node (3-14) at (3,-1,4) {};    
    \node (34-1) at (3,4,-1) {};    
    \node (4-13) at (4,-1,3) {};    
    \node (43-1) at (4,3,-1) {};  
    \draw[blue] (123) -- (132) -- (231) -- (321) -- (312) -- (213) -- (123) -- (024) -- (015) -- (105) -- (204) -- (213);
    \draw[blue] (321) -- (420) -- (510) -- (501) -- (402) -- (312);
    \draw[blue] (132) -- (042) -- (051) -- (150) -- (240) -- (231);
    \draw[blue] (402) -- (4-13) -- (3-14) -- (204);
    \draw[blue] (024) -- (-134) -- (-143) -- (042);
    \draw[blue] (240) -- (34-1) -- (43-1) -- (420);
    \draw[->, orange, ultra thick] (h2) -- (h1);
    \draw[->, skyblue, ultra thick] (h2) -- (h3);
    \draw[->, bluishgreen, ultra thick] (h4) -- (h3);
    \draw[->, orange, ultra thick] (h4) -- (h5);
    \draw[->, skyblue, ultra thick] (h6) -- (h5);
    \draw[->, bluishgreen, ultra thick] (h6) -- (h1);
    \end{tikzpicture}
    &
    \begin{tikzpicture}[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center}]
    %Nauru
    \coordinate (h1) at ($2*(3,2,1)+2*(2,3,1)$);
    \coordinate (h2) at ($2*(2,3,1)+2*(1,3,2)$);
    \coordinate (h3) at ($2*(1,3,2)+2*(1,2,3)$);
    \coordinate (h4) at ($2*(1,2,3)+2*(2,1,3)$);
    \coordinate (h5) at ($2*(2,1,3)+2*(3,1,2)$);
    \coordinate (h6) at ($2*(3,1,2)+2*(3,2,1)$);
    \draw[draw=white, fill=black!10] (h1) -- (h2) -- (h3) -- (h4) -- (h5) -- (h6) -- cycle;
    \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;
    \node (123) at (1,2,3) {};    
    \node (132) at (1,3,2) {};    
    \node (213) at (2,1,3) {};    
    \node (231) at (2,3,1) {};    
    \node (312) at (3,1,2) {};    
    \node (321) at (3,2,1) {};    
    \node (024) at (0,2,4) {};    
    \node (042) at (0,4,2) {};    
    \node (204) at (2,0,4) {};    
    \node (240) at (2,4,0) {};    
    \node (402) at (4,0,2) {};    
    \node (420) at (4,2,0) {};   
    \node (015) at (0,1,5) {};    
    \node (051) at (0,5,1) {};    
    \node (105) at (1,0,5) {};    
    \node (150) at (1,5,0) {};    
    \node (501) at (5,0,1) {};    
    \node (510) at (5,1,0) {};  
    \node (-134) at (-1,3,4) {};    
    \node (-143) at (-1,4,3) {};    
    \node (3-14) at (3,-1,4) {};    
    \node (34-1) at (3,4,-1) {};    
    \node (4-13) at (4,-1,3) {};    
    \node (43-1) at (4,3,-1) {};  
    \draw[blue] (123) -- (132) -- (231) -- (321) -- (312) -- (213) -- (123) -- (024) -- (015) -- (105) -- (204) -- (213);
    \draw[blue] (321) -- (420) -- (510) -- (501) -- (402) -- (312);
    \draw[blue] (132) -- (042) -- (051) -- (150) -- (240) -- (231);
    \draw[blue] (402) -- (4-13) -- (3-14) -- (204);
    \draw[blue] (024) -- (-134) -- (-143) -- (042);
    \draw[blue] (240) -- (34-1) -- (43-1) -- (420);
    \draw[blue] (510) -- (5.5,1,-0.5);
    \draw[blue] (501) -- (5.5,-0.5,1);
    \draw[blue] (015) -- (-0.5,1,5.5);
    \draw[blue] (105) -- (1,-0.5,5.5);
    \draw[blue] (150) -- (1,5.5,-0.5);
    \draw[blue] (051) -- (-0.5,5.5,1);
    \draw[blue] (3-14) -- (3,-1.5,4.5);
    \draw[blue] (4-13) -- (4.5,-1.5,3);
    \draw[blue] (43-1) -- (4.5,3,-1.5);
    \draw[blue] (34-1) -- (3,4.5,-1.5);
    \draw[blue] (-143) -- (-1.5,4.5,3);
    \draw[blue] (-134) -- (-1.5,3,4.5);
    \draw[->, orange, ultra thick] (h2) -- (h1);
    \draw[->, skyblue, ultra thick] (h2) -- (h3);
    \draw[->, bluishgreen, ultra thick] (h4) -- (h3);
    \draw[->, orange, ultra thick] (h4) -- (h5);
    \draw[->, skyblue, ultra thick] (h6) -- (h5);
    \draw[->, bluishgreen, ultra thick] (h6) -- (h1);
    \end{tikzpicture}
    &
    \begin{tikzpicture}[x={(240:2cm)},
            	y={(0:2cm)},
            	z={(120:2cm)},scale=0.17,
                every node/.append style={circle,draw=black,fill=white,inner sep=1.8pt,align=center}]
    %F26A
    \coordinate (h1) at ($1*(3,2,1)+3*(2,3,1)$);
    \coordinate (h2) at ($1*(2,3,1)+3*(1,3,2)$);
    \coordinate (h3) at ($1*(1,3,2)+3*(1,2,3)$);
    \coordinate (h4) at ($1*(1,2,3)+3*(2,1,3)$);
    \coordinate (h5) at ($1*(2,1,3)+3*(3,1,2)$);
    \coordinate (h6) at ($1*(3,1,2)+3*(3,2,1)$);
    \draw[draw=white, fill=black!10] (h1) -- (h2) -- (h3) -- (h4) -- (h5) -- (h6) -- cycle;
    \draw[draw=white, fill=blue!20] (1,2,3) -- (2,1,3) -- (3,1,2) -- (3,2,1) -- (2,3,1) -- (1,3,2) -- cycle;
    \node (123) at (1,2,3) {};    
    \node (132) at (1,3,2) {};    
    \node (213) at (2,1,3) {};    
    \node (231) at (2,3,1) {};    
    \node (312) at (3,1,2) {};    
    \node (321) at (3,2,1) {};    
    \node (024) at (0,2,4) {};    
    \node (042) at (0,4,2) {};    
    \node (204) at (2,0,4) {};    
    \node (240) at (2,4,0) {};    
    \node (402) at (4,0,2) {};    
    \node (420) at (4,2,0) {};   
    \node (015) at (0,1,5) {};    
    \node (051) at (0,5,1) {};    
    \node (105) at (1,0,5) {};    
    \node (150) at (1,5,0) {};    
    \node (501) at (5,0,1) {};    
    \node (510) at (5,1,0) {};  
    \node (-134) at (-1,3,4) {};    
    \node (-143) at (-1,4,3) {};    
    \node (3-14) at (3,-1,4) {};    
    \node (34-1) at (3,4,-1) {};    
    \node (4-13) at (4,-1,3) {};    
    \node (43-1) at (4,3,-1) {};  
    \node (-116) at (-1,1,6) {};    
    \node (-161) at (-1,6,1) {};    
    \node (1-16) at (1,-1,6) {};    
    \node (16-1) at (1,6,-1) {};    
    \node (6-11) at (6,-1,1) {};    
    \node (61-1) at (6,1,-1) {};  
    \node (-235) at (-2,3,5) {};    
    \node (-253) at (-2,5,3) {};    
    \node (3-25) at (3,-2,5) {};    
    \node (35-2) at (3,5,-2) {};    
    \node (5-23) at (5,-2,3) {};    
    \node (53-2) at (5,3,-2) {};  
    \node (-226) at (-2,2,6) {};    
    \node (-262) at (-2,6,2) {};    
    \node (2-26) at (2,-2,6) {};    
    \node (26-2) at (2,6,-2) {};    
    \node (6-22) at (6,-2,2) {};    
    \node (62-2) at (6,2,-2) {};  
    \draw[blue] (123) -- (132) -- (231) -- (321) -- (312) -- (213) -- (123) -- (024) -- (015) -- (105) -- (204) -- (213);
    \draw[blue] (321) -- (420) -- (510) -- (501) -- (402) -- (312);
    \draw[blue] (132) -- (042) -- (051) -- (150) -- (240) -- (231);
    \draw[blue] (402) -- (4-13) -- (3-14) -- (204);
    \draw[blue] (024) -- (-134) -- (-143) -- (042);
    \draw[blue] (240) -- (34-1) -- (43-1) -- (420);
    \draw[blue] (510) -- (61-1) -- (62-2);
    \draw[blue] (501) -- (6-11) -- (6-22);
    \draw[blue] (015) -- (-116) -- (-226);
    \draw[blue] (105) -- (1-16) -- (2-26);
    \draw[blue] (150) -- (16-1) -- (26-2);
    \draw[blue] (051) -- (-161) -- (-262);
    \draw[blue] (3-14) -- (3-25) -- (2-26);
    \draw[blue] (4-13) -- (5-23) -- (6-22);
    \draw[blue] (43-1) -- (53-2) -- (62-2);
    \draw[blue] (34-1) -- (35-2) -- (26-2);
    \draw[blue] (-143) -- (-253) -- (-262);
    \draw[blue] (-134) -- (-235) -- (-226);

    
    \draw[->, bluishgreen, ultra thick] (61-1) -- (62-2) -- (53-2);
    \draw[->, bluishgreen, ultra thick] (53-2) -- (43-1) -- (34-1);
    \draw[bluishgreen, ultra thick] (34-1) -- (35-2);
    
    \draw[->, orange, ultra thick] (1-16) -- (2-26) -- (3-25);
    \draw[->, orange, ultra thick] (3-25) -- (3-14) -- (4-13);
    \draw[orange, ultra thick] (4-13) -- (5-23);
    
    \draw[->, skyblue, ultra thick] (-161) -- (-262) -- (-253);
    \draw[->, skyblue, ultra thick] (-253) -- (-143) -- (-134);
    \draw[skyblue, ultra thick] (-134) -- (-235);
    
    \draw[->, orange, ultra thick] (-161) -- (051) -- (150);
    \draw[->, orange, ultra thick] (150) -- (16-1) -- (26-2);
    \draw[orange, ultra thick] (26-2)-- (35-2);
    
    \draw[->, skyblue, ultra thick] (61-1) -- (510) -- (501);
    \draw[->, skyblue, ultra thick] (501) -- (6-11) -- (6-22);
    \draw[skyblue, ultra thick] (6-22)-- (5-23);
    
    \draw[->, bluishgreen, ultra thick] (1-16) -- (105) -- (015);
    \draw[->, bluishgreen, ultra thick] (015) -- (-116) -- (-226);
    \draw[bluishgreen, ultra thick] (-226)-- (-235);
    \end{tikzpicture}
    \\
    Pappus
    &
    Nauru
    &
    F26A 
    \\
$\begin{pmatrix}
    3  &  & \\ 
       & 3 &   \\
      &   & 3  \\
\end{pmatrix}$&
$\begin{pmatrix}
    2  & -2 & \\ 
       &  2 & -2  \\
    -2 &    & 2   \\
\end{pmatrix}$& 
$\begin{pmatrix}
    3  & -1 &  \\ 
       &  3 & -1 \\
    -1 &    & 3 \\
\end{pmatrix}$    \\
    \end{tabular}

