[IEEE 2011 International Conference on E-Business and E-Government (ICEE) - Shanghai, China (2011.05.6-2011.05.8)] 2011 International Conference on E-Business and E-Government (ICEE) - Study of the relationship between voluntary assurance of internal control and quality of information disclosure — An empirical analysis of a-share companies listed in main board of Shenzhen stock exchange from 2008 to 2009