 The 1st century CE "Periplus of the Erythraean Sea", among other documents, also reports early commercial exchanges between traders inhabiting city-states on the northern Somalia littoral with Himyarite and Sabaean merchants.Numerous artefacts dating from this period have been uncovered in Somalia, such as at the Damo site in the northeastern Puntland region.In the Middle Ages, the Somali Sultanates often recruited troops from Yemen's Hadhramaut region.