@book { VarietyandVariability,
    title = "Variety and Variability",
    author = "Imran {Ho-Abdullah}",
    year = "2011",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    doi = "10.3726/978-3-0351-0167-6",
    url = "https://www.peterlang.com/document/1052312"
}