Hansen, Kaj. 1981. “A GEOLOGICAL MAP OF ETHIOPIA AND SOMALIA (1973) 1:2.000.000 and Comment With a Map of Major Landforms. By Giovanni Merla . Et Al. Firenze 1979, VIII, 95 s., Ill. & 2 Kort I Lomme, 34 Cm, $ 60.-. Pergamon Press Ltd., Oxford”. Geografisk Tidsskrift 81 (januar). https://tidsskrift.dk/geografisktidsskrift/article/view/45237.