APA

Organisation for Economic Co-operation and Development (OECD), . (1999). The state of the environment. Paris: OECD.

Chicago

Organisation for Economic Co-operation and Development (OECD), . 1999. The state of the environment. Paris: OECD.

Harvard

Organisation for Economic Co-operation and Development (OECD), . (1999). The state of the environment. Paris: OECD.

MLA

Organisation for Economic Co-operation and Development (OECD), . The state of the environment. Paris: OECD. 1999.