Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
va thieu » va thiet, va hieu, va tieu
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
cao hoi » cau hoi, co hoi, cao hoc
va dan » ca dan, va dao, va dau
vai va » mai va, dai va, hai va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (thu sach)) ky nang cao hoi. ((hieu van) OR (hieu va)) pham thuc va dan vai va thieu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (thu sach)) ky nang cao hoi. ((hieu van) OR (hieu va)) pham thuc va dan vai va thieu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (thu sach)) ky nang cao hoi. ((hieu van) OR (hieu va)) pham thuc va dan vai va thieu".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (thu sach)) ky nang cao hoi. ((hieu van) OR (hieu va)) pham thuc va dan vai va thieu*.