Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
cau theo » cau tao
hoc sach » hoc sinh, hoc cac, hoc anh
lang van » dang van, tang van, hoang van
thuc va » thuc vat, thuc dan, thuc day
dau vai » dau va, dau hai, dau tai
hieu va » lieu va, hieu qua
van hoi » van hoa, van hoc, van hoe
va dau » va dao
y lang » o lang, _ lang, tay lang
va am » va lam, va cam

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