* LiteOS: A Unix-like Operating System 
** http://lanterns.eecs.utk.edu/software/liteos/
** https://code.google.com/archive/p/liteos/

* Contiki
** http://www.contiki-os.org/
** https://github.com/contiki-os/contiki
** Wikipedia
*** https://en.wikipedia.org/wiki/Contiki
*** https://ja.wikipedia.org/wiki/Contiki

* FreeRTOS
** https://www.freertos.org/
** Wikipedia
*** https://en.wikipedia.org/wiki/FreeRTOS
*** https://ja.wikipedia.org/wiki/FreeRTOS

* TinyOS
** https://github.com/tinyos/tinyos-main
** Wikipedia
*** https://en.wikipedia.org/wiki/TinyOS

* Comparison of real-time operating systems
** https://en.wikipedia.org/wiki/Comparison_of_real-time_operating_systems