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
thuc dan » thuc hanh, hoc dan, thuc vat
tu sach » su sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
dan dai » dat dai, dan dat, dan da
thiet » thieu

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 dan ((dan dai) OR (can dai)) va thiet~.
• 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 dan ((dan dai) OR (can dai)) va thiet.
• 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 dan ((dan dai) OR (can dai)) va thiet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang cao hoi. hieu van pham thuc dan ((dan dai) OR (can dai)) va thiet*.