We are grateful to our reviewers:

Katarina Eggensperger (U. Freiburg, Germany)

Hugo Jair Escalante (IANOE, Mexico)

Sergio Escalera (U. Barcelona, Spain)

Isabelle Guyon (UPSud, U. Paris-Saclay, France, and ChaLearn, USA)

Vincent Lemaire (Orange Labs, France.)

Richard Lippmann (MIT, USA.)

Fabrice Popineau (Centrale Supelec, France)

Mehreen Saeed (U. Lahore, Pakistan)

Zoltan Szabo (CMAP, Ecole Polytechnique, France)

Evelyne Viegas (Microsoft Research, USA)