Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
dua ban » cua ban, qua ban, mua ban
hai cua » thai cua, dai cua, hoi cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang xa) or (nang x)) hoi. hieu van nam ((dua ban) OR (dia ban)) thanh hai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang xa) OR (nang x)) hoi. hieu van nam ((dua ban) OR (dia ban)) thanh hai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang xa) or (nang x)) hoi. hieu van nam ((dua ban) OR (dia ban)) thanh hai cua viet".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang xa) or (nang x)) hoi. hieu van nam ((dua ban) OR (dia ban)) thanh hai cua viet*.