Here are a few references:
- The MicroPython web page at http://micropython.org
- The MicroPython project on Kickstarter at https://www.kickstarter.com/projects/214379695/micro-python-python-for-microcontrollers
- An article in microcontrollers on PC Mag at https://www.pcmag.com/encyclopedia/term/46924/microcontroller
- The Adafruit learning guide on CircuitPython at https://learn.adafruit.com/welcome-to-circuitpython/what-is-circuitpython
- The CircuitPython official documentation at https://circuitpython.readthedocs.io