Perhaps you should try some spelling variations:
nam trung » nam trong, tai trung, ba trung
dat tren » dat trong, dua tren
thu sach » thuat sach, thuoc sach, thu hoach
nam truc » nam truoc, nam thuc, nam thuoc
tu sach » su sach, te sach, tu cach
hieu ve » hieu va, hieu van
cao hoc » co hoc, cho hoc, chat hoc
va dan » ca dan, va dao, va dau
ca dat » cai dat, ca dao, ca dan

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