https://blog.mindvalley.com/how-to-wake-up-early/
https://www.sleepfoundation.org/articles/what-circadian-rhythm
https://www.sharecare.com/health/sleep-basics/what-happens-wake-up
https://www.tuck.com/waking-up/
https://science.howstuffworks.com/life/inside-the-mind/human-brain/sleep2.htm
https://www.healthline.com/health/morning-fatigue-remedies#3
https://www.lifehack.org/404417/6-ways-to-wake-up-early-without-feeling-tired
https://www.redeemingproductivity.com/how-to-wake-up-early-and-not-feel-tired/
https://www.sciencedirect.com/science/article/abs/pii/S0272494409000838
http://colossalsleep.com/waking-up-tired/