Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
lang van » dang van, tang van, hoang van
nam thuc » nam thuoc, am thuc, nam thu
cau theo » cau thi, cau tao
hoc sach » hoc sinh, hoc cac, hoc anh
van hoi » van hoa, van hoc, van hoe
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dau vai » dau va, dau tai
dau hai » dai hai, dau ha, cau hai
y lang » o lang, _ lang, tay lang
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: ((toc sach) or (hoc sach)) y lang van hoi. hieu va nam thuc va ((dau vai) OR (dau hai)) cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) y lang van hoi. hieu va nam thuc va ((dau vai) OR (dau hai)) cau theo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) y lang van hoi. hieu va nam thuc va ((dau vai) OR (dau hai)) cau theo".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) y lang van hoi. hieu va nam thuc va ((dau vai) OR (dau hai)) cau theo*.