Perhaps you should try some spelling variations:
american scientists » american societies
robert walser » robert warren, robert watson, robert winter
robert walker » robert hawker, robertson walker, robert warren
robert walt » robert watt, robert wait, robert walter

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 walker))) OR (robert walt)) (american scientists).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((robert walser) OR (robert walker))) or (robert walt)) (american scientists)".
• Adding a wildcard symbol may retrieve word variants: ((((robert walser) OR (robert walker))) or (robert walt)) (american scientists)*.