Perhaps you should try some spelling variations:
dinh dai » dinh dat, sinh dai, dinh dao
dan dinh » dang dinh, doan dinh, van dinh
thuc dan » thuc hanh, hoc dan, thuc vat
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
su sach » vu sach
so sach » so sanh, bo sach, co sach
tang xa » trang xa, tang ma, lang xa
hieu ve » hieu va
cua te » cua tu
y tang » ky tang, 6 tang, 7 tang

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (so sach)) y tang xa hoi. ((hieu ve) OR (hieu van)) cam thuc dan dinh dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) y tang xa hoi. ((hieu ve) OR (hieu van)) cam thuc dan dinh dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) y tang xa hoi. ((hieu ve) OR (hieu van)) cam thuc dan dinh dai cua te".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) y tang xa hoi. ((hieu ve) OR (hieu van)) cam thuc dan dinh dai cua te*.