Roos, G. (1935). Comparative researches on the variation of the constituents of coal of one seam from south Limburg: The Netherlands. Van Aelst Bros.
Lua i Stíl Chicago (17ú heag.)Roos, Gerrit. Comparative Researches on the Variation of the Constituents of Coal of One Seam from South Limburg: The Netherlands. Maastricht: Van Aelst Bros, 1935.
Lua MLA (8ú heag.)Roos, Gerrit. Comparative Researches on the Variation of the Constituents of Coal of One Seam from South Limburg: The Netherlands. Van Aelst Bros, 1935.
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