Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
thu sach » thuat sach, thuoc sach, thu hoach
danh vai » danh sai, danh va, doanh van
vat danh » va danh, van danh, luat danh
nam thuc » nam thuoc, am thuc, nam thu
vai cau » va cau, van cau, vai cac
hieu va » lieu va, hieu qua
tu sach » su sach, te sach, tu cach
nang ma » tang ma, sang ma, nang cao
va nam » van nam, ha nam, va nay

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 ma) or (nang x)) hoi. hieu va nam thuc vat danh vai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) y ((nang ma) OR (nang x)) hoi. hieu va nam thuc vat danh vai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) y ((nang ma) or (nang x)) hoi. hieu va nam thuc vat danh vai cau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) y ((nang ma) or (nang x)) hoi. hieu va nam thuc vat danh vai cau tren*.