Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
va thanh » gia thanh, va tinh, le thanh
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
lang xa » lang ha, dang xay, lang van
sach ty » sach y, sach tu, xach tay
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc ((sach ty) or (sach thu)) lang xa hoi. hieu van nam thuc ((va thanh) OR (ban thanh)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach ty) OR (sach thu)) lang xa hoi. hieu van nam thuc ((va thanh) OR (ban thanh)) va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc ((sach ty) or (sach thu)) lang xa hoi. hieu van nam thuc ((va thanh) OR (ban thanh)) va cua tre".
• Adding a wildcard symbol may retrieve word variants: toc ((sach ty) or (sach thu)) lang xa hoi. hieu van nam thuc ((va thanh) OR (ban thanh)) va cua tre*.