Perhaps you should try some spelling variations:
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
cua viet » ca viet, hoa viet, cua dieu
tu sach » thu sach, su sach, te sach
sach tu » sach thu, cach tu, sach ty
nam duc » nam duoc, pham duc, nam thuc
va hanh » van hanh, va thanh, va danh

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 tu ((dang xay) or (nang x)) hoi. hieu van nam duc va hanh hai ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tu ((dang xay) OR (nang x)) hoi. hieu van nam duc va hanh hai ((cua viet) OR (cua vat)).
• Adding a wildcard symbol may retrieve word variants: tu sach tu ((dang xay) or (nang x)) hoi. hieu van nam duc va hanh hai ((cua viet) or (cua vat))*.