The Bronze Age of Dhofar not only has parallels with Yemen to the west but to the north across the Rub al Khali. Surveys in 1976-77 of the Jabrin oasis just north of the Rub al Khali, revealed wedge-shaped structures and tombs with concentric circles. Other sites such as Umm an Nussi have clear ties with northern Oman and southern Mesopotamia.