Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam thu
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
va nam » van nam, ha nam, va nay
dan va » doan va, dan ca, han va

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) or (hoc sach)) ky tang xa hoi. hieu va nam thuc vat ((dan va) OR (ban va)) cau tao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky tang xa hoi. hieu va nam thuc vat ((dan va) OR (ban va)) cau tao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) ky tang xa hoi. hieu va nam thuc vat ((dan va) OR (ban va)) cau tao".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky tang xa hoi. hieu va nam thuc vat ((dan va) OR (ban va)) cau tao*.