Perhaps you should try some spelling variations:
"viewed studium, vorkurs mathematik" » "reviewed studies, vorkurs mathematik", "viewed studium, vorkurs mathematical"
"vieweg studium, vorkurs mathematik" » "vieweg studium, vorkurs mathematical"

Try widening your search to All Fields.

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"vieweg studium, vorkurs mathematik\") OR (\"viewed studium, vorkurs mathematik\"))".
• Removing quotes may allow a broader search: (( vieweg studium, vorkurs mathematik ) OR ( viewed studium, vorkurs mathematik )).
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