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

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) or (co hoi)). hieu ve ((cam tuc) or (am thuc)) va dan ca ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((cao hoi) OR (co hoi)). hieu ve ((cam tuc) OR (am thuc)) va dan ca ca tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((cao hoi) or (co hoi)). hieu ve ((cam tuc) or (am thuc)) va dan ca ca tren*.