Cita APA (7th ed.)

ebrary, Inc, Hill, J., & Gale, T. (2009). Ecotourism and environmental sustainability: Principles and practice. Ashgate.

Cita Chicago (17th ed.)

ebrary, Inc, Jennifer Hill, i Tim Gale. Ecotourism and Environmental Sustainability: Principles and Practice. Farnham, England ; Burlington, VT: Ashgate, 2009.

Cita MLA (9th ed.)

ebrary, Inc, et al. Ecotourism and Environmental Sustainability: Principles and Practice. Ashgate, 2009.