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