Woulfe, Peter (). „Experiments on some mineral substances”. Philosophical Transactions of the Royal Society of London. 69: 11–34. doi:10.1098/rstl.1779.0004. On pages 29–34, Woulfe analyzed a sample of a mineral from Joachimsthal (now: Jáchymov, Czech Republic) (see p. 30). On p. 31, Woulfe stated that the mineral contained "a new earth", and on pp. 32 and 34, he stated that it contained "some other earth".
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Woulfe, Peter (). „Experiments on some mineral substances”. Philosophical Transactions of the Royal Society of London. 69: 11–34. doi:10.1098/rstl.1779.0004. On pages 29–34, Woulfe analyzed a sample of a mineral from Joachimsthal (now: Jáchymov, Czech Republic) (see p. 30). On p. 31, Woulfe stated that the mineral contained "a new earth", and on pp. 32 and 34, he stated that it contained "some other earth".
