United Nations Environment Programme Industry and Environment. (1998). Ecolabels in the tourism industry. UNEP.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रUnited Nations Environment Programme Industry and Environment. Ecolabels in the Tourism Industry. Paris, France: UNEP, 1998.
एमएलए (9वां संस्करण) प्रशस्ति पत्रUnited Nations Environment Programme Industry and Environment. Ecolabels in the Tourism Industry. UNEP, 1998.
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