Instance optimal Crouzeix-Raviart adaptive finite element methods for   the Poisson and Stokes problems
  We extend the ideas of Diening, Kreuzer, and Stevenson [Instance optimality of the adaptive maximum strategy, Found. Comput. Math. (2015)], from conforming approximations of the Poisson problem to nonconforming Crouzeix-Raviart approximations of the Poisson and the Stokes problem in 2D. As a consequence, we obtain instance optimality of an AFEM with a modified maximum marking strategy. 
Christian Kreuzer, Mira Schedensack
math.NA