The palaeontological literature on the Early Miocene of the northern Sperrgebiet comprises over 50 papers. There was a short lived flurry of activity between 1920 and 1930, after which there was extremely little published until the last decade of the 20th century. The few papers that appeared in the 1950's, 1960's and 1970's usually referred to the Sperrgebiet fossils in passing, or while comparing them with material from East Africa. Half the total number of papers has appeared since 1990.