Finally I bought two books about the four color theorem: “**Four Colors Suffice: How the Map Problem Was Solved**” by Robin Wilson e Ian Stewart; and the “**The Four-Color Theorem: History, Topological Foundations, and Idea of Proof**” by Rudolf Fritsch and Gerda Fritsch.

I’am in the middle of reading the first one and I want to go back to the basics and use the method used by Kempe when he belived he had solved the problem.

**With these differences**: Instead of shrinking down to a point the faces with less than 6 edges, I will remove from these faces one edge at a time, from F2, F3. From the F4 faces I will remove two opposite edges. And from F5 or F5-F5 or F5-F6 (unavoidable sets) I will try to remove two or more edges. This way, after having reduced the map to two single faces (including the ocean), I will restore the edges in reverse order, this way always dealing with 3-regular planar graphs, and instead of applying Kempe’s chain color switching to the faces, I will consider also Tait coloring of the edges and Kempe’s chain color switching to the egdes.

**Follow the arrow to visualize the steps:**

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## About stefanutti

V: "Do you know me?"
S: "yes."
V: "No you don't."
S: "Okay."
V: "Did you see my picture in the paper?"
S: "Yes."
V: "No you didn't."
S: "I don't even get the paper."

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