Hertlein, K. M., Weeks, G. R., & Gambescia, N. (2015). Systemic sex therapy (2nd ed.). Routledge. Read Chapters 1 and 2. These chapters will give you a sense of where sex therapy is now and what the ethical concerns are when working with a client using sex therapy.
Jones, A. C., Johnson, N. C., Wenglein, S., & Elshershaby, S. T. (2019). The state of sex research in MFT and family studies literature: A seventeen-year content analysis. Journal of Marital and Family Therapy, 45(2), 275–295. This article looks at the research that has been completed within MFT and family studies journals to show that MFTs need more experience and focus on sexual issues for their clients.
Firestone, R. W., Firestone, L. A., & Catlett, J. (2006). What is healthy sexuality? In Sex and love in intimate relationships (pp. 11–27). American Psychological Association. This chapter explores what is normal about healthy sex, and how do you, as a therapist, decide?