Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
van tac » van thac, van tai, van tan
tac dat » tac da, tac dao, tac dau
dat ban » bat ban, da ban, day ban
sach ty » sach tu, sach thu, xach tay
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach y) or (sach ty)) nang ma hoi. hieu van tac dat ban thanh ((vi cua) OR (di cua)) vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach y) OR (sach ty)) nang ma hoi. hieu van tac dat ban thanh ((vi cua) OR (di cua)) vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach y) or (sach ty)) nang ma hoi. hieu van tac dat ban thanh ((vi cua) OR (di cua)) vat".
• Adding a wildcard symbol may retrieve word variants: thu ((sach y) or (sach ty)) nang ma hoi. hieu van tac dat ban thanh ((vi cua) OR (di cua)) vat*.