@unpublished{049r_PREPRINT,
 Author = {Amal Alphonse and Michael Hinterm\"{u}ller and Carlos N. Rautenberg},
 Note = {Preprint SPP1962-049r},
 Title = {Directional Differentiability for Elliptic Quasi-variational Inequalities of Obstacle Type},
 Month = {11},
 Year = {2019}}