Perhaps you should try some spelling variations:
"german colonial archives" » "german colonial archive", "german colonial narratives", "german cultural archives", "german colonialism archives", "germany colonies archives", "american colonial archives"
"german fluvial archives" » "german official archives", "german fluvial facies", "german fluvial regimes", "germany fluvial archives"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"german fluvial archives\") OR (\"german colonial archives\"))".
• Removing quotes may allow a broader search: (( german fluvial archives ) OR ( german colonial archives )).
• Adding a wildcard symbol may retrieve word variants: (("german fluvial archives") OR ("german colonial archives"))*.