Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
sach ky » sac ky, sach y, sach ty
vai cua » dai cua, lai cua, bai cua
hai cua » thai cua, dai cua, hoi cua
thuc va » thuc dan, thuc day

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 va) OR (thuc vat)) dan ((vai cua) or (hai 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 va) OR (thuc vat)) dan ((vai cua) OR (hai cua)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky dang xay hoi. hieu van nam ((thuc va) OR (thuc vat)) dan ((vai cua) or (hai cua)) triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang xay hoi. hieu van nam ((thuc va) OR (thuc vat)) dan ((vai cua) or (hai cua)) triet*.