Operating Systems

https://github.com/cfenollosa/os-tutorial

https://github.com/cfenollosa/os-tutorial
http://www.cs.bham.ac.uk/%7Eexr/lectures/opsys/10_11/lectures/os-dev.pdf
http://www.cs.bham.ac.uk/~exr/lectures/opsys/10_11/lectures/os-dev.pdf
http://mikeos.sourceforge.net/write-your-own-os.html

http://www.brokenthorn.com/Resources/OSDevIndex.html

http://littleosbook.github.io/

https://github.com/SamyPesse/How-to-Make-a-Computer-Operating-System.git

http://www.jamesmolloy.co.uk/index.html

Books
The Art of Linux KerneL Design Illustrating the Operating System Design Principle and Implementation
International Standard Book Number-13: 978-1-4665-1804-9, 978-1-4665-1803-2

LINUX APPLIANCE DESIGN
ISBN-10: 1593271409
ISBN-13: 978-1593271404

Xv6
https://github.com/mit-pdos/xv6-public
https://pdos.csail.mit.edu/6.828/2012/xv6.html
http://blog.regehr.org/archives/1114

RetroBSD
http://retrobsd.org/wiki/doku.php