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Article History

Received: 23 April 2018

Accepted: 19 July 2018

First Online: 26 July 2018

Compliance with ethical standards

:

: The authors declare that they have no conflict of interest.

: The first author gathered most of the reference literature and wrote the manuscript. The other authors read the manuscript several times, suggested major revisions for it and contributed with literature reference suggestions. The contributions of the 2nd, 3rd and 4th author can be seen as equal.