Perhaps you should try some spelling variations:
trinh vat » trinh van, trinh luat, sinh vat
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
tinh va » tich va, trinh van, tinh gia
tu sach » thu sach, su sach, te sach
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
thu va » thuc va, thue va, tu va

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 thu ((nang ma) or (nang x)) hoi. hieu van nam thu va ((tinh va) or (trinh vat)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu ((nang ma) OR (nang x)) hoi. hieu van nam thu va ((tinh va) OR (trinh vat)) cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach thu ((nang ma) or (nang x)) hoi. hieu van nam thu va ((tinh va) or (trinh vat)) cua tre*.