
https://www.wto.org/english/res_e/reser_e/ullbergpresentation_e.pdf

https://www.ifri.org/sites/default/files/atoms/files/d._puhl_vfa_33_deutschland_die_zeitenwende_und_die_zukunft_de.pdf

http://www.cesifo-group.de/ifoHome/publications/working-papers/CESifoWP/CESifoWPdetails?wp_num=6448&CESifoWP.search=+