Perhaps you should try some spelling variations:
thanh de » hanh de, thanh ve, thanh do
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 tac, cac nuoc
cac tu » cac thu, cach tu, cac du
de hoa » de khoa, de hoan, do hoa

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) OR (cac tu)) gia thanh de hoa 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) OR (cac tu)) gia thanh de hoa 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) OR (cac tu)) gia thanh de hoa viet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) ky nang cao hoi. hieu va ((cac tuc) OR (cac tu)) gia thanh de hoa viet*.