Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, cau treo
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
ca tren » cu tren, la tren, co tren
cam tuc » cam xuc, cam tu, dam thuc
hieu ve » hieu va, hieu van
cao hoi » cau hoi, co hoi, cao hoc
va dan » ca dan, va dao, va dau

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 ky nang cao hoi. hieu ve ((cam tuc) or (nam thuc)) va dan ca ((cau tren) OR (ca tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang cao hoi. hieu ve ((cam tuc) OR (nam thuc)) va dan ca ((cau tren) OR (ca tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang cao hoi. hieu ve ((cam tuc) or (nam thuc)) va dan ca ((cau tren) OR (ca tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang cao hoi. hieu ve ((cam tuc) or (nam thuc)) va dan ca ((cau tren) OR (ca tren))*.