Copyright and Open Access License: In 2017 the license is changed from Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0) to Creative Commons Attribution 4.0 International (CC BY) License.

All articles will be offered under the terms of the Creative Commons Attribution 4.0 International (CC BY) License ( which permits unrestricted use, distribution, and reproduction in any medium, provided appropriate credit is given to the original author(s) and the source.

The corresponding author should complete and sign the copyright form and then send it by email to or

 The copyright form is available to download by clicking on authorship- copyright form.