Matthies, K., & Timm, H. (1998). World commodity prices 1998 - 1999.
Lua i Stíl Chicago (17ú heag.)Matthies, Klaus, agus Hans-Joachim Timm. World Commodity Prices 1998 - 1999. Hamburg, 1998.
Lua MLA (8ú heag.)Matthies, Klaus, agus Hans-Joachim Timm. World Commodity Prices 1998 - 1999. 1998.
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