In recent years there has been a huge evolution of mobile
systems and many people nowadays have moved several activities
from their computer to their smartphone or tablet,
thanks to the ease of use and convenience to carry the device
with them everywhere [12]. Indeed, mobile devices have
exceeded computer sales for the first time in 2012. The
different ergonomics of these devices w.r.t. personal computers
or notebooks has generated new approaches in order
to search for and provide the desired information. Smaller