Strabo iii. p. 155. ἀντὶ δὲ νομίσματος οἱ λίαν ἐν βάθει φορτίων ἀμοιβῇ χρώνται ἢ τοῦ ἀργύρου ἐλάγματος ἀποτέμνοντες διδόασιν.

Gordon Lang, Travels in Western Africa (1825), Prefatory Note.

The specimen figured was brought home about 30 years ago and is now in the Edinburgh Museum of Science and Art.

The specimens here figured are in the splendid collection of my friend Mr R. Day, of Cork.

This information I owe to Lieut. Troup.

I am indebted to Messrs James Booth and Co. for this information.

Dapper Description de l’Afrique (Amsterdam, 1686) p. 367. “Le bois rouge de Majumba et la pao de Hiengo de Benguela tiennent aussi le lieu de monnaie: on en coupe des morceaux d’un pied de long; on leur met une certaine taxe selon laquelle le prix des vivres se règle.”

Peter Kolben, Present state of the Cape of Good Hope, p. 262.

R. W. Felkin, “Notes on the Madi or Moru Tribe of Central Africa,” Transactions of Royal Society of Edinburgh, Vol. XII. p. 303 seqq.