Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
hang di » hang doi, hang vi, hang dien
va hang » van hang, va nang, va lang
cac dat » cac dan, cai dat, cac dai
van cac » van hac, van cau, van bac
sang ma » tang ma, sang tao, mang may
nang ma » tang ma, nang cao, mang may
tu sach » su sach, te sach, tu cach
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) OR (tu sach)) ty ((nang ma) or (sang ma)) hoi. hieu van cac dat va hang di cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (tu sach)) ty ((nang ma) OR (sang ma)) hoi. hieu van cac dat va hang di cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) OR (tu sach)) ty ((nang ma) or (sang ma)) hoi. hieu van cac dat va hang di cua vat".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) OR (tu sach)) ty ((nang ma) or (sang ma)) hoi. hieu van cac dat va hang di cua vat*.