We wish to emphasize the fact that so far our investigations have concentrated on documenting large bodies of data covering a number of linguistic units in an area which - as we hope to have demonstrated - displays a highly complex linguistic and ethnic structure. Our aim in the above remarks is essentially to throw out a challenge. In order to be able to interpret this situation in terms of the historic development of this zone of compression, further investigations are required, particularly regarding linguistic interference between Chadic and Niger-Congo languages in the south, as well as between Chadic and Nilo-Saharan languages, particularly Kanuri in the north-east and Songhay in the north-west. Ultimately, questions like the followin...