Wilson R. Robin. (2003). Four Colours Suffice. How the Map Problem was Solved. London, Penguin Books, 2003.
Chicago-viite (17. p.)Wilson R. Robin. Four Colours Suffice. How the Map Problem Was Solved. London, Penguin Books, 2003, 2003.
MLA-viite (9. p.)Wilson R. Robin. Four Colours Suffice. How the Map Problem Was Solved. London, Penguin Books, 2003, 2003.
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