Yandex, Leo Tolstoy, 16, Moscow, Russia;Kontur Labs and Ural Federal University, Fonvizina 3-27, Yekaterinburg, Russia;National Research University Higher School of Economics (HSE), Pokrovskii bd 11, Moscow, Russia;University of Amsterdam, Turfdraagsterpad 9, Amsterdam, The Netherlands;Knowledge Media Institute, The Open University, Walton Hall, Milton Keynes, UK