Cita APA (7a ed.)

McDonald Klimek, M., Obert, K. B., & Steinhauer, K. (2005). Estill voice training system. Estill Voice Training Systems International.

Cita Chicago Style (17a ed.)

McDonald Klimek, Mary, Kerrie B. Obert, y Kimberly Steinhauer. Estill Voice Training System. [Pittsburgh, Pa.]: Estill Voice Training Systems International, 2005.

Cita MLA (9a ed.)

McDonald Klimek, Mary, et al. Estill Voice Training System. Estill Voice Training Systems International, 2005.