Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
nam thuc » nam thuoc, am thuc, nam thu
thu sach » thuat sach, thuoc sach, thu hoach
nang mai » nang ma, nang tai, lang mai
thuc van » thuc vat, thuc dan, thuc va
tu sach » su sach, te sach, tu cach
mai hoi » mai khoi, dai hoi, lai hoi
qua nam » quan nam, cua nam, quang nam
y nang » ky nang, ly nang, v nang
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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) or (thu sach)) y nang mai hoi. hieu qua nam thuc van thanh ((vi cua) OR (di cua)) quoc~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) y nang mai hoi. hieu qua nam thuc van thanh ((vi cua) OR (di cua)) quoc.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) y nang mai hoi. hieu qua nam thuc van thanh ((vi cua) OR (di cua)) quoc".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) y nang mai hoi. hieu qua nam thuc van thanh ((vi cua) OR (di cua)) quoc*.