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