The authors thank the editor, an associate editor, three anonymous referees, Fabio Bellini, Aleš Černý, An Chen, Jan Dhaene, Paul Embrechts, Paul Glasserman, Pablo Koch-Medina, Dimitrios Konstantinides, Henry Lam, Jean-Gabriel Lauzier, Fabio Macherroni, Massimo Marinacci, Cosimo Munari, Alexander Schied, Qihe Tang, Stan Uryasev, Peter Wakker, and Zuoquan Xu for helpful comments and discussions on an earlier version of the paper.