Published in Transactions of the Royal Society of South Africa, in 1909, in volume 1, issue 1, pages 125
Published in Transactions of the Royal Society of South Africa, in 1909, in volume 1, issue 1, pages 126
Published in Transactions of the Royal Society of South Africa, in 1909, in volume 1, issue 1, pages 127-128
Published in Transactions of the Royal Society of South Africa, in 1909, in volume 1, issue 1, pages 315-319