@book { ThevisualizationofforeignlanguagevocabularyinCALL,
    title = "The visualization of foreign language vocabulary in CALL",
    author = "Angela {Heidemann}",
    year = "1996",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1083130"
}