Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
tai cua » thai cua, tri cua, dai cua
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
ve nam » he nam, va nam, le nam

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

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