Bike sharing systems are spreading throughout the world, being used by more and more people every day. Anyway, a higher diffusion means more bikes to manage and reorganise among bike sharing stations to guarantee a good quality of the service. Up to today, it does not exist a universally accepted algorithm to rebalance the distribution of bikes over a dock-based bike sharing system. From an extensive review of the current state of the art, it appears that, although bike sharing is a very active research field, there are few papers about dynamic rebalancing algorithms and all the existing ones are based on mathematical models of bike sharing stations.