Matematica 3 Scola primara [dir. dil project e concept general ed. tudestga: Bernhard Keller ... et al.] ; [menadra dil project ed. sursilvana: Josy Marie Künzler]
Bibliothekskatalog der Kantonsbibliothek Graubünden: https://www.opac.gr.ch/discovery/fulldisplay?context=L&vid=41BGR_INST:41BGR_V1&search_scope=MyInstitution&tab=LibraryCatalog&docid=alma990005092500206696