Below are the weblinks from the endnotes in Sex Purpose Love with short descriptions were applicable:
2. Social relationships—both quantity and quality—affect mental health, health behavior, physical health, and mortality risk.
www.ncbi.nlm.nih.gov/pmc/articles/PMC3150158/
Happiness and health aren’t a result of wealth, fame or working hard, but come instead from the quality of our relationships.
www.mentalhealth.org.uk/publications/relationships-21st-century-forgotten-foundation-mental-health-and-wellbeing
People with a sense of purpose had a 15 percent lower risk of death, compared with those who said they were more or less aimless
www.npr.org/sections/health-shots/2014/07/28/334447274/people-who-feel-they-have-a-purpose-in-life-live-longer
4. https://en.wikipedia.org/wiki/Stoicism
5.
6.