@unpublished{ Oswald:2016, author = {Peter Oswald}, title = {Nonconforming P1 elements on distorted triangulations: Lower bounds for the discrete energy norm error}, annote = {article, inspreprint}, note = {INS Preprint No. 1618}, inspreprintnum= {1618}, year = {2016}, pdf = {http://www.ins.uni-bonn.de/people/oswald/InsPreprint1618.pdf} }