Funding for this research was provided by:
Volkswagen Foundation (91474, 91474, 91474)
German Academic Exchange Service (57129429)
Received: 16 April 2019
Accepted: 22 October 2019
First Online: 8 November 2019
Ethics approval and consent to participate
: The study and its procedure were approved by each of the ethical review committees of Bielefeld University in Germany and Koya University in the Kurdistan region of Iraq.
: Not applicable.
: The authors declare that they have no competing interests.