Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
tu sach » su sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
thuc va » thuc vat, thuc dan, thuc day
dan dai » dat dai, can dai, dan dat
va dan » ca dan, va dao, va dau
dai va » mai va

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

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