Simpson, J. B. (1900). Capital and labour in coal mining during the past two hundred years. R. Robinson.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रSimpson, John Bell. Capital and Labour in Coal Mining During the Past Two Hundred Years. Newcastle-upon-Tyre: R. Robinson, 1900.
एमएलए (8वां संस्करण) प्रशस्ति पत्रSimpson, John Bell. Capital and Labour in Coal Mining During the Past Two Hundred Years. R. Robinson, 1900.
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