References:
- https://www.nationalgeographic.com/science/health-and-human-body/human-body/heart/
- https://www.fi.edu/heart-engine-of-life
- http://www.math.niu.edu/~kong/360/014.pd
- https://www.heartmath.org/articles-of-the-heart/science-of-the-heart/the-energetic-heart-is-unfolding/
- http://kidshealth.org/en/kids/heart.html#
- http://www.innerbody.com/image/card01.html
- http://www.texasheart.org/HIC/Anatomy/anatomy2.cfm