Köpke, G., & Grundheber-Pilgram, A. (1990). The centenary of May Day ; Portrait of the European Trade Union Confederation (ETUC). Brussels: ETUI.
Lua i Stíl Chicago (17ú heag.)Köpke, Günter, agus Alfons Grundheber-Pilgram. The Centenary of May Day ; Portrait of the European Trade Union Confederation (ETUC). Brussels: ETUI, 1990.
Lua MLA (8ú heag.)Köpke, Günter, agus Alfons Grundheber-Pilgram. The Centenary of May Day ; Portrait of the European Trade Union Confederation (ETUC). Brussels: ETUI, 1990.
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