Institut Géographique National – 2048 Ouest, 2408 Est, 2407 ouest, 2407 Est. Two of these date back to the 80s (donated by a friend who had updated!) but the roads have not changed in the areas of importance. You need all four to cover The Somme properly and some people I know have cut them up and stuck the four relevant areas back together to make one. I haven’t quite had the courage to do that yet. A proper map is invaluable, even in this age of GPS, online maps etc… These copies have been extensively used but have lasted well and have years still to give!