Map of the Periglacial Region in Japan at the Height of the Last Glaciation  about 20,000 years ago
Davison A, Chiba S, Barton NH, Clarke B. (2005) "Speciation and Gene Flow between Snails of Opposite Chirality" (in English). PLoS Biology 3 (9, e282). doi:10.1371/journal.pbio.0030282 [1]
Davison A, Chiba S, Barton NH, Clarke B. (Vectorized for Wikipedia Italy Graphic Lab by User:MacMoreno )