Perhaps you should try some spelling variations:
thuc day » thuc dan, thuc vat
hanh vai » hanh vi, hanh va, hanh tai
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach
thuc va » thuc vat, thuc dan
sach ky » sac ky, sach y, sach ty
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 x) or (dang xay)) hoi. hieu van nam ((thuc va) or (thuc day)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang x) OR (dang xay)) hoi. hieu van nam ((thuc va) OR (thuc day)) hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang x) or (dang xay)) hoi. hieu van nam ((thuc va) or (thuc day)) hanh vai cua tre*.