Perhaps you should try some spelling variations:
hoang hai » hoang thi, hoang van
dat hoang » dat hang, dang hoang, dai khoang
cua viet » ca viet, hoa viet, cua vat
nam thuc » nam thuoc, nam thu, nam tu
hai cua » thai cua, dai cua, hoi cua
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
hieu he » hieu ve, hiem he, hieu le

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang xa) OR (nang ma)) hoi. hieu he ((nam thuc) or (am thuc)) dat hoang hai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang xa) OR (nang ma)) hoi. hieu he ((nam thuc) OR (am thuc)) dat hoang hai cua viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky ((nang xa) OR (nang ma)) hoi. hieu he ((nam thuc) or (am thuc)) dat hoang hai cua viet*".