“…Among these extensions there are results on the non-symmetric formulation for the potential equation with variable coefficients [OS13,Ste11], non-linearities [AFF + 13, FFKP15], for elasticity [FFKP15,Ste13], and for boundary value problems [GHS12,OS14]. In addition, similar results have been reported on related coupling formulations [AFF + 13, GHS12] and the DG-BEM coupling [HS15]. We want to mention that the counterpart to the non-symmetric coupling is the so called the symmetric coupling first introduces in [Cos87].…”