Singh, R. K. (2003). Eco-Tourism and Sustainable development.
Chicago Edition CitationSingh, Ravisankar Kumar. Eco-Tourism and Sustainable Development. Abhijeet publishers,Delhi, 2003.
MLA引文Singh, Ravisankar Kumar. Eco-Tourism and Sustainable Development. 2003.
警告：这些引文格式不一定是100％准确.