Text and Data Mining valid from 2019-07-29
Received: 5 March 2019
Accepted: 18 July 2019
First Online: 29 July 2019
Ethics approval and consent to participate
: Written consent was obtained from all subjects without ethical approval because of the national survey design (IRB No. 2013-07CON-03-4C, 2013-12EXP-03-5C).
: Not applicable.
: The authors declare that they have no competing interests.