Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh doi » thanh doi, hanh noi, hang doi
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
sang ma » tang ma, sang tao, mang may
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
nang ma » tang ma, nang cao, mang may
cua tre » cuu tre, cua triet, dua tren
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach y ((nang ma) or (sang ma)) hoi. hieu van nam thuc va hanh doi ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((nang ma) OR (sang ma)) hoi. hieu van nam thuc va hanh doi ((cua tre) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: toc sach y ((nang ma) or (sang ma)) hoi. hieu van nam thuc va hanh doi ((cua tre) or (cua te))*.