Lewis M. B., Bowler P. J. Botulinum Toxin Cosmetic Therapy Correlates with a More Positive Mood // Journal of Cosmetic Dermatology. 2009. March. Vol. 8. No. 1. Pp. 24–26 // ; Marzoli D. et al. Sun-Induced Frowning Fosters Aggressive Feelings // Cognition & Emotion. 2013. Vol. 27. No. 8. Pp. 1513–1521 // .