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