Weizsacker, E. v., Lovins, A. B., & Lovins, L. H. (1997). Factor four: Doubling wealth, halving resource use. Earthscan.
Lua i Stíl Chicago (17ú heag.)Weizsacker, Ernst von, Amory B. Lovins, agus L. Hunter Lovins. Factor Four: Doubling Wealth, Halving Resource Use. London: Earthscan, 1997.
Lua MLA (9ú heag.)Weizsacker, Ernst von, et al. Factor Four: Doubling Wealth, Halving Resource Use. Earthscan, 1997.
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