Before revision:  We propose a class of dominant strategy incentive compatible (DSIC)  and ex post individual rational (EPIR) mechanisms that balance the budget and approximates the first-best welfare level when the number of participants is large .
After revision:  We propose a class of informationally robust, dominant-strategy incentive compatible (DSIC) and ex post individual rational (EPIR) mechanisms that balance the budget and approximates the first-best welfare level when the number of participants is large .