Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam tu
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
xay hoi » xa hoi, tay hoi, cay phoi
vai cua » hai cua, lai cua, bai cua
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 ky dang xay hoi. hieu van ((nam thuc) or (nam thu)) va dau ((vai cua) or (dai cua)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang xay hoi. hieu van ((nam thuc) OR (nam thu)) va dau ((vai cua) OR (dai cua)) triet.
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang xay hoi. hieu van ((nam thuc) or (nam thu)) va dau ((vai cua) or (dai cua)) triet*.