Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
thuc day » thuc vat
thuc dan » thuc hanh, hoc dan, thuc vat
danh sai » dung sai, danh bat, danh dau
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
sai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet

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 xa hoi. ((hieu van) or (lieu va)) chat ((thuc day) or (thuc dan)) danh sai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. ((hieu van) OR (lieu va)) chat ((thuc day) OR (thuc dan)) danh sai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((hieu van) or (lieu va)) chat ((thuc day) or (thuc dan)) danh sai cua tre*.