An open textbook is a dynamic project. New developments, such as relevant new publications, can be added, urls go dead and new ones have to be found, and reader feedback in the form of comments to sections of the book get added almost on a daily basis. This second edition includes the changes made to the first edition.

Here I will keep track of changes, using 10 October 2019, when this second edition was first made available in its ‘final’ form, as the baseline.