Klok, Frederikus A.
Versteeg, Henri H.
Verschoor, Arie J.
Huisman, Menno V.
Article History
Received: 29 October 2018
Revised: 28 November 2018
Accepted: 3 December 2018
First Online: 30 January 2019
Competing interests
: The authors declare no competing interests.
: This work is published under the standard license to publish agreement. After 12 months the work will become freely available and the license terms will switch to a Creative Commons Attribution 4.0 International (CC BY 4.0).