Perhaps you should try some spelling variations:
thien van » thi van
hanh doi » thanh doi, hanh noi, hang doi
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, lieu va, hieu ve
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
doi cua » dai cua, hoi cua
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet

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 y ((mang may) or (nang ma)) hoi. ((hieu van) OR (thien van)) cam thuc dan hanh doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((mang may) OR (nang ma)) hoi. ((hieu van) OR (thien van)) cam thuc dan hanh doi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((mang may) or (nang ma)) hoi. ((hieu van) OR (thien van)) cam thuc dan hanh doi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach y ((mang may) or (nang ma)) hoi. ((hieu van) OR (thien van)) cam thuc dan hanh doi cua tre*.