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Openstax offers free access to english textbooks and learning environments including exercises. The ebooks can be downloaded as PDFs or used online. Logged in users can create highlights and annotations.
We particularly recommend the following ebooks:
Chemistry 2e
Physics Vol. 1 (mechanics, sound, oscillations, and waves)
Physics Vol. 2 (thermodynamics, electricity and magnetism)
Physics Vol. 3 (optics, quantum mechanics, solid state and particle physics)
We wish you all good luck with the exams!