Arpaci-Dusseau, R. H., & Arpaci-Dusseau, A. C. (n.d.). Operating Systems: Three Easy Pieces - A free online textbook. University of Wisconsin-Madison. https://pages.cs.wisc.edu/~remzi/OSTEP/
MIT OpenCourseWare: Operating System Engineering - Lecture notes, assignments, and exams from MIT's course on operating system engineering. https://ocw.mit.edu/courses/6-828-operating-system-engineering-fall-2012/