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

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 (((medical scientists) OR (physical scientists))).
• Adding a wildcard symbol may retrieve word variants: robert walser (((medical scientists) or (physical scientists)))*.