[1] Imperial Coll London, Dept Comp, London SW7 2AZ, England
[2] Univ Svizzera Italiana, Inst Computat Sci, CH-6900 Lugano, Switzerland
[3] Qualcomm Technol Netherlands BV, NL-6546 Nijmegen, Netherlands
[4] Google DeepMind, London AB101, England
[5] Mohamed bin Zayed Univ Artificial Intelligence, Abu Dhabi 51133, U Arab Emirates
[6] Stanford Univ, Comp Sci Dept, Stanford, CA 94305 USA
[7] Univ Cambridge, Comp Lab, William Gates Bldg, Cambridge CB3 0FD, England
[8] NYU, Courant Inst Math Sci, New York, NY 10012 USA
[9] Univ Siena, Dept Informat Engn & Math, I-53100 Siena, SI, Italy