         petersen:
             insert : "graphs.PetersenGraph()"
         random_graph:
-            insert : "graphs.RandomGNM(15, 20)  # 15 vertices and 20 edges"
+            insert : "g=graphs.RandomGNM(15, 20)  # 15 vertices and 20 edges\ng.incidence_matrix()"
         chromatic_number:
             insert : "graphs.PetersenGraph().chromatic_number()"
         auto_group_graph:

                    """
        icosahedron :
            insert : "show(icosahedron(color='green', opacity=.5, mesh=3), spin=1)"
        cube :
            insert : """
                        show(cube(color=['red', 'blue', 'green'], frame_thickness=2,
                                  frame_color='brown', opacity=0.8), frame=False)
                    """
        plot_text3d:
            insert : 'text3d("Text in 3D", (1,1, 1), color="darkred", fontsize=20)'
        graphs:

                     [["&part; Differentiate", "#differentiate", "Differentiate a function"],
                      ["&int; Numerical Integral",      "#nintegrate",     "Numerically integrate a function"]
                      ["$f(x,y) = \\cdots $ - Symbolic Function",      "#symbolic_function",     "Define a symbolic function"]
                      ["&int; Symbolic Integral",      "#integrate",     "Integrate a function"],
                      ["Interact Plots"],
                      ["Interactive f(x)", "#interact_fx"]
                    ]]
    sage_linalg = ["Linear", "Linear Algebra",
                  [
