Acknowledgements

Every effort has been made to contact copyright holders. If any have been inadvertently overlooked the publishers will be pleased to make the necessary arrangements at the first opportunity.

Important: *** against any of the acknowledgements below means that the wording has been dictated by the rights holder/publisher, and cannot be changed.

Grateful acknowledgement is made to the following sources:

Figure 1: Isaac Mao. This file is licensed under the Creative Commons Attribution Licence http://creativecommons.org/ licenses/ by/ 2.0/ [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

Figure 2: ***© Business Model Alchemist, This file is licensed under the Creative Commons Attribution-Share Alike Licence http://creativecommons.org/ licenses/ by-sa/ 3.0/

Figure 3: Image by Michal Jarmoluk from Pixabay

Figure 4: Image by mightybutton from Pixabay

Figure 5: © melpomen / 123 Royalty Free