Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
can cau » van cau, ban cau, ca cau
hieu ve » hieu va, hieu van
tu sach » thu sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
su sach » so sach, vu sach
cam tuc » cam xuc, cam tu, nam thuc
ve cam » ve cham, ve cac, va cam
va dan » va dao, va dau, va dap
ca dan » cac dan, ca dao

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