BERTRAM AT CAETEC DG7BBA BAASKE-SCHOTT ET. AL., 15 Jan 2018 https://books.google.de/books?id=aABqCQAAQBAJ
BERTRAM AT CAETEC DG7BBA BAASKE-SCHOTT ET. AL., 12 Jan 2018 https://books.google.de/books?id=aABqCQAAQBAJ