A scooter with one free-swaying rear-wheel set respectively located at rear end of the two fixed holding rods. The rear-wheel sets can sway freely to make the two rear wheels move leftward and rightward; hence, when operator's feet exert strength on said two fixed holding rods, the two rear wheels will...http://www.google.fr/patents/US7549655?utm_source=gb-gplus-shareBrevet US7549655 - Scooter
