Perhaps you should try some spelling variations:
among actors » among doctors, among acholi, among donors
patients 1.5 » patients 10.5, patients 14.5, patients 3.5
yang yang » wang yang, wang yan
1.5 among » 1.8 among, 2.15 among, 19 among
yan yang » yao yang, dan yang, tan yang
aan de » jan de
van de » van der, van den

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: lang ((yan yang) OR (yang yang)) ((aan de) OR (van de)) patients 1.5 among actors ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "lang ((yan yang) OR (yang yang)) ((aan de) or (van de)) patients 1.5 among actors ;~".
• Adding a wildcard symbol may retrieve word variants: lang ((yan yang) OR (yang yang)) ((aan de) or (van de)) patients 1.5 among actors ;*.