sentences:  DG methods for elliptic problems were already developed in a paper by Garth Baker in the setting of 4th order equations in 1977.A more complete account of the historical development and an introduction to DG methods for elliptic problems is given in a publication by Arnold, Brezzi, Cockburn and Marini.A number of research directions and challenges on DG methods are collected in the proceedings volume edited by Cockburn, Karniadakis and Shu.