motivation:
Mihailov - 2016 - How to Learn Math
    https://www.youtube.com/watch?v=UM4SRQsIqok
Hmelinsky - 2016 - Everyone has Math Abilities
    https://www.youtube.com/watch?v=B4eJMy54yuU
    https://www.youtube.com/watch?v=R8L_SAsmUd0
Kozlov Maxim Viktorovich - 2012 - Why Children do not like Math
    https://www.youtube.com/watch?v=SXQ_7m79ZeM