Integration of Power to Gas/Power to Liquids into the ongoing transformation process / Umweltbundesamt ; authors: Katja Purr, Dirk Osiek, Martin Lange, Kirsten Adlunger und Andreas Burger, Benno Hain, Kai Kuhnhenn, Harry Lehmann, Lars Mönch, Klaus Müschen, Christopher Proske, Martin Schmied, Carla Vollmer ; translation by: Richard Holmes and Gabriele Coan