Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
lang van » tang van, hoang van, giang van
nam thuc » nam thuoc, am thuc, nam thu
dang van » hoang van, hang va
cau theo » cau thi, cau tao
hoc sach » hoc sinh, hoc cac, hoc anh
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dau vai » dau va, dau hai, dau tai
vai cau » va cau, van cau, vai cac
va nam » van nam, ha nam, va nay
va dau » va dao

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)) y ((lang van) OR (dang van)) hoi. hieu va nam thuc va dau vai cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) y ((lang van) OR (dang van)) hoi. hieu va nam thuc va dau vai cau theo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) y ((lang van) OR (dang van)) hoi. hieu va nam thuc va dau vai cau theo".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) y ((lang van) OR (dang van)) hoi. hieu va nam thuc va dau vai cau theo*.