Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam tu
cau theo » cau thi, cau tao
xay hoi » xa hoi, tay hoi, cay phoi
dan vai » dan va, dan tai, dan vat
vai cau » va cau, van cau, vai cac
y dang » ky dang, 2 dang, _ dang
va dan » ca dan, va dao, va dau

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