According to a review of the 181 peer-reviewed papers on 100% renewable energy which were published until 2018, "[t]he great majority of all publications highlights the technical feasibility and economic viability of 100% RE systems." While there are still many publications which focus on electricity only, there is a growing number of papers that cover different energy sectors and sector-coupled, integrated energy systems. This cross-sectoral, holistic approach is seen as an important feature of 100% renewable energy systems and is based on the assumption "that the best solutions can be found only if one focuses on the synergies between the sectors" of the energy system such as electricity, heat, transport or industry.[10]