Textbooks are important resources to support learners. In order to explain structures and relations of real existing objects, expository texts are frequently complemented by illustrations. A key role of this complement play annotations which identify illustrations and their parts by their technical terms and consequently may enable the establishment of visual links between expository texts and the depictions. However, the depiction of spatial objects may lead to unintentional ambiguities and due to economic constraints illustrators may be forced to design illustrations as general as possible....