My 2 sisters and I are planning to visit Shenzhen,China for sight seeing purposes on Sept 3, 2010..Its a round trip plam..we will be coming in at dawn of sept 3 and will be exiting on the evening of the same day..we believe that we need to secure a tourist visa before entrance to shenzhen..what shall we do?...can you recommend the most convenient way to secure a tourist visa?...thank you very much..