VNET [21Vianet] SC 13G/A: (Original Filing)
[JOINT FILING AGREEMENT Dated: February 6, 2013 ATRIX ARTNERS HINA M Matrix China Management I, L.P. Matrix China I GP GP, Ltd. David Su Director ATRIX ARTNERS HINA M Matrix China Management I, L.P. Matrix China I GP GP, Ltd. David Su Director ATRIX HINA ANAGEMENT M Matrix China I GP GP, Ltd.] [CUSIP No. 90138A 10 3 1. Names of Reporting Persons Matrix Partners China I, L.P. 2. Check the Appropriate Box if a Member of a Group (See Instructions) ¨ (a) ¨ (b) 3. SEC Use Only 4. Citizenship or Place of Organization]