Lecture notes on Viscosity Solutions for fully nonlinear 2nd order PDE   and applications to Calculus of Variations in $L^\infty$
  The purpose of these expository notes is to give a quick and elementary, yet rigorous, presentation of the rudiments of the theory of Viscosity Solutions for fully nonlinear 2nd order PDE, with applications to Calculus of Variations in the space $L^\infty$. 
Nikos Katzourakis
math.AP