Perhaps you should try some spelling variations:
american scientists » american societies
robert walser » robert walker, robert warren, robert watson
robert walter » robert walters, roberts walter, robert walker

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((robert walser) OR (robert walter)) (american scientists).
• Adding a wildcard symbol may retrieve word variants: ((robert walser) or (robert walter)) (american scientists)*.