Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
danh vai » danh sai, danh va, doanh van
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
cu tren » tu tren, dua tren
va nam » van nam, ha nam, va nay
vai cu » vai cua, van cu

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 y ((nang ma) or (nang x)) hoi. hieu va nam thuc va danh vai cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang ma) OR (nang x)) hoi. hieu va nam thuc va danh vai cu tren.
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang ma) or (nang x)) hoi. hieu va nam thuc va danh vai cu tren*.