Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cua cau » cua cac, cua chu, cua cay
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
tu sach » thu sach, su sach, te sach
cao hoc » co hoc, cho hoc, chat hoc
cao hoi » cau hoi, co hoi, tao hoi
cam tuc » cam xuc, cam tu, nam thuc
ve cam » ve cham, ve cac, va cam
va dan » ca dan, va dao, va dap
va dau » va 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 ky nang ((cao hoi) OR (cao hoc)). hieu ve cam tuc ((va dan) or (va dau)) cua cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((cao hoi) OR (cao hoc)). hieu ve cam tuc ((va dan) OR (va dau)) cua cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((cao hoi) OR (cao hoc)). hieu ve cam tuc ((va dan) or (va dau)) cua cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((cao hoi) OR (cao hoc)). hieu ve cam tuc ((va dan) or (va dau)) cua cau tren*.