Text and Data Mining valid from 2019-11-14
Received: 4 April 2019
Revised: 29 September 2019
Accepted: 2 October 2019
First Online: 14 November 2019
Compliance with ethical standards
: The study was approved by the local ethics committee and in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards, following parental informed consent.
: The authors declare that they have no conflict of interest.