1. Międzynarodowe badanie ilościowe, na zlecenie Unilever, ResearchNow: październik 2019, próba 2000 Polaków
2. Dr. Vivek Murthy, Harvard Business Review 2017: https://boston.cbslocal.com/2018/06/21/loneliness-rises-health-epidemic/
3. Dr. Robert Waldinger, Harvard Study of Adult Development, https://www.cnbc.com/2017/10/31/this-harvard-study-reveals-how-you-can-be-happier-and-more-successful.html