Perhaps you should try some spelling variations:
dan hanh » dang hanh, dan khanh, dan thanh
so sach » so sanh, bo sach, co sach
qua cac » cua cac
cac hoc » cach hoc, cac hop, bac hoc
hanh di » hanh vi, hanh de, hang di
ca viet » va viet, co viet, hoa viet
v nang » va nang, vu nang, van nang
di ca » di cau, di cua, doi ca

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ((v nang) or (van ban)) xa hoi. hieu qua cac hoc dan hanh di ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((v nang) OR (van ban)) xa hoi. hieu qua cac hoc dan hanh di ca viet.
• Adding a wildcard symbol may retrieve word variants: so sach ((v nang) or (van ban)) xa hoi. hieu qua cac hoc dan hanh di ca viet*.