المصدر: National Geographic Magazine, 1977, Vol. 152, No. 6, P. 706.

المصدر: National Geographic Magazine, 1976, Vol. 150, No. 6, P. 708-709.

المصدر: National Geographic Magazine, 1977, Vol. 151, No. 3, P. 272-273.

المصدر: National Geographic Magazine, 1976, Vol. 149, No. 6, P. 710-711.

المصدر: National Geographic Magazine, 1977, Vol. 151, No. 2, P. 144.

المصدر: National Geographic Magazine, 1975, Vol. 148, No. 5, P. 566.

المصدر: National Geographic Magazine, 1981, Vol. 160, No. 6, P. 698.

المصدر: National Geographic Magazine, 1981, Vol. 160, No. 2, P. 124.

المصدر: National Geographic Magazine, 1973, Vol. 144, No. 2, P. 136.

المصدر: National Geographic Magazine, 1972, Vol. 141, No. 1.