McDonald Klimek, M., Obert, K. B., & Steinhauer, K. (2005). Estill voice training system. Estill Voice Training Systems International.
Chicago-viite (17. p.)McDonald Klimek, Mary, Kerrie B. Obert, ja Kimberly Steinhauer. Estill Voice Training System. [Pittsburgh, Pa.]: Estill Voice Training Systems International, 2005.
MLA-viite (9. p.)McDonald Klimek, Mary, et al. Estill Voice Training System. Estill Voice Training Systems International, 2005.
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