Thayer, R. L. (1994). Gray World, Green Heart Technology, Nature, And The Sustainable Landscape Robert L. Thayer. John Wiley & Sons.
Lua i Stíl Chicago (17ú heag.)Thayer, Robert L. Gray World, Green Heart Technology, Nature, And The Sustainable Landscape Robert L. Thayer. John Wiley & Sons, 1994.
Lua MLA (8ú heag.)Thayer, Robert L. Gray World, Green Heart Technology, Nature, And The Sustainable Landscape Robert L. Thayer. John Wiley & Sons, 1994.
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