Perhaps you should try some spelling variations:
treatment challenge » treatment challenges, greatest challenge, recruitment challenge
challenge funding » challenge finding, challenges finding, challenge facing
4.1 treatment » 3.1 treatment, 2.1 treatment, 7.1 treatment
funding among » bonding among, building among, jumping among
among di » among hiv, among idp, among _
nan yan » nan ya, wang yan, qian yan
yang xi » yang di, yang yi, yang jui
era 4.1 » era 2.1, era 3.1, era 1.1

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: ((nan yan) OR (yang xi))5g era 4.1 treatment challenge funding among di ;~.
• Adding a wildcard symbol may retrieve word variants: ((nan yan) or (yang xi))5g era 4.1 treatment challenge funding among di ;*.