Perhaps you should try some spelling variations:
vu khach » vu khanh, vu khac, vay khach
vu sach » vu bach, su sach
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
nang o » nang co, nang ho, nang ro
cac tu » cac thu, cach tu, cac du
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((vu sach) or (vu khach)) ky nang o hoi. hieu va cac tu va hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (vu khach)) ky nang o hoi. hieu va cac tu va hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (vu khach)) ky nang o hoi. hieu va cac tu va hanh vi ((cua tre) or (cuu tre))*.