Text and Data Mining valid from 2018-08-30
Received: 19 April 2018
Accepted: 13 August 2018
First Online: 30 August 2018
Compliance with ethical guidelines
: P. Bhogal and M. Aguilar Pérez serve as proctors and consultants for phenox. H. Henkes is a co-founder and shareholder of phenox. M. AlMatter, V. Hellstern, H. Bäzner and O. Ganslandt declare that they have no competing interests.
: For this type of retrospective study formal approval is not required.