Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
vu khach » vu khanh, vu khac, vay khach
hieu ve » hieu va, hieu van
vu sach » vu bach, su sach
vi cau » va cau, ve cau, di cau
ve ban » te ban, va ban, ve bao
x hoi » xa hoi, o hoi, x ho
bo va » bao va, do va, co va
so va » so van, so vat, su va

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 x hoi. hieu ve ban ((bo va) or (so va)) hanh vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (vu khach)) ky nang x hoi. hieu ve ban ((bo va) OR (so va)) hanh vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) OR (vu khach)) ky nang x hoi. hieu ve ban ((bo va) or (so va)) hanh vi cau tren".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) OR (vu khach)) ky nang x hoi. hieu ve ban ((bo va) or (so va)) hanh vi cau tren*.