Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, lanh dao
nam thuc » nam thuoc, am thuc, nam thu
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
va vanh » va van, va danh, va hanh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
ty hang » ly hang, ty xang, thi hang
ty lang » tay lang, ty xang, tu lang
va nam » van nam, ha nam, va nay
cua tu » cua tuc, cua su, cua cu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty lang) or (ty hang)) xa hoi. hieu va nam thuc va vanh dai ((cua tre) or (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty lang) OR (ty hang)) xa hoi. hieu va nam thuc va vanh dai ((cua tre) OR (cua tu)).
• Adding a wildcard symbol may retrieve word variants: su sach ((ty lang) or (ty hang)) xa hoi. hieu va nam thuc va vanh dai ((cua tre) or (cua tu))*.