Perhaps you should try some spelling variations:
american scientists » american societies
medical scientists » biomedical scientists, physical scientists, medical sciences
robert walser » robert walker, robert warren, robert watson
robert watt » robert watson, robert white

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