Modern Romance by 
The Oxford Handbook of Emerging Adulthood by 
Adolescent Psychology Around the World by 
Emerging Adulthood by Arnett, J. J. (2000). Emerging adulthood: A theory of development from the late teens through the twenties. American Psychologist, 55(5), 469–480. https://doi.org/10.1037/0003-066X.55.5.469
Mehta, C. M., Arnett, J. J., Palmer, C. G., & Nelson, L. J. (2020). Established adulthood: A new conception of ages 30 to 45. American Psychologist, 75(4), 431–444. https://doi.apa.org/doiLanding?doi=10.1037%2Famp0000600