URL https://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/'Unique_Forms_of_Continuity_in_Space',_1913_bronze_by_Umberto_Boccioni.jpg/1200px-'Unique_Forms_of_Continuity_in_Space',_1913_bronze_by_Umberto_Boccioni.jpg
URL2 https://ja.wikipedia.org/wiki/空間における連続性の唯一の形態
