Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cua viet » ca viet, cua vat, cua dieu
sach hoi » sach doi, sach moi, cach thoi
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
hanh di » hanh vi, hanh de, hang di
sach lo » sach dao, sach doi, sach moi
sang ma » tang ma, nang ma, sang tao
ma hoi » mai hoi, xa hoi, ma hoa

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach lo) or (sach hoi)) sang ma hoi. hieu van nam thuc van hanh di ((cua viet) OR (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach lo) OR (sach hoi)) sang ma hoi. hieu van nam thuc van hanh di ((cua viet) OR (hoa viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach lo) or (sach hoi)) sang ma hoi. hieu van nam thuc van hanh di ((cua viet) OR (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach lo) or (sach hoi)) sang ma hoi. hieu van nam thuc van hanh di ((cua viet) OR (hoa viet))*.