Glenn Shafer is University Professor at Rutgers University. Vladimir Vovk is Professor in the Department of Computer Science at Royal Holloway, University of London. Shafer and Vovk are the authors of Probability and Finance: It's Only a Game, published by Wiley and co-authors of Algorithmic Learning in a Random World. Shafer's other previous books include A Mathematical Theory of Evidence and The Art of Causal Conjecture.