In an example with two objects and four bidders, some of which have superadditive values, we characterize the equilibria of a simultaneous ascending auction and compare the revenue and efficiency generated with ones generated by the sequential, the one-shot simultaneous, and the Vickrey-Clarke-Groves auctions.
Albano, G.-L., Germano, F., & Lovo, S. (1999). A comparison of standard multi-unit auctions with synergies (CORE Discussion Papers 1999/52). https://hdl.handle.net/2078.5/128154