Tessier, V., Normandin, L., Ensink, K., & Fonagy, P. (1969). Fact or fiction? A longitudinal study of play and the development of reflective functioning. Bulletin of the Menninger Clinic, 80(1), 60-79. https://doi.org/10.1521/bumc.2016.80.1.60 (Original work published 1969)