Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
va tinh » may tinh
tinh de » tinh da, sinh de, tinh he
ca viet » va viet, hoa viet, san viet
co viet » so viet, o viet, hoc viet
tuc va » thuc va, truc va, tuc xa

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 hoach)) ky nang cao hoi. hieu va cac tuc va tinh de ((ca viet) OR (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu hoach)) ky nang cao hoi. hieu va cac tuc va tinh de ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu hoach)) ky nang cao hoi. hieu va cac tuc va tinh de ((ca viet) OR (co viet))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) ky nang cao hoi. hieu va cac tuc va tinh de ((ca viet) OR (co viet))*.