Perhaps you should try some spelling variations:
american scientists » american societies
robert walter » robert walters, roberts walter, robert walker
robert walsh » robert walser, robert walsers, robert watson
robert welch » robert weech, robert wrench, robert wells
robert walt » robert watt, robert wait, robert watts

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