不落窠臼地思考of a box with some dots in it, and the idea is to connect all the dots by using only four lines. You can work on that puzzle, but the only way to solve
拉蒙特-多爾蒂地球觀測所doublets," Science, 309(2005): 1357–1360. M. Tharp, "Connect the dots: Mapping the seafloor and discovering the mid-ocean ridge," L. Lippsett, (ed.), Lamont–Doherty