Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
thuc dan » thuc hanh, thuc vat
tu sach » su sach, te sach, tu cach
dan dai » dat dai, can dai, dan dat
dai va » mai va
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 cau hoi. hieu van pham ((thuc dan) OR (hoc dan)) dan dai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang cau hoi. hieu van pham ((thuc dan) OR (hoc dan)) dan dai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang cau hoi. hieu van pham ((thuc dan) OR (hoc dan)) dan dai va thiet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang cau hoi. hieu van pham ((thuc dan) OR (hoc dan)) dan dai va thiet*.