As a result of current measures to combat the COVID-19 virus, Cambridge University Press has decided to place a large number of e-books and journal articles in open access free of charge until the end of May. These works may provide interesting source material for those who write a bachelor's or master's thesis or paper or for those looking for additional source material when studying a course unit.
For a more extensive news item, check this link: https://www.cambridge.org/about-us/covid-19/
For a list of works by sub-area, check the following link: https://www.cambridge.org/core/browse-subjects
Any work that says "Access" (in green) instead of "Get access" can be viewed online in HTML.