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

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