Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
nam thuc » nam thuoc, am thuc, nam thu
hieu ve » hieu va, hieu van
tu sach » thu sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
ty nang » ky nang, ty xang, ty hang
su sach » so sach, vu sach
va dan » ca dan, va dao, va dap
va dau » va dao
ca cau » cua cau, cac cau, can cau
ve nam » he nam, va nam, le nam

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