Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
hieu van » hieu va, thien van, lieu va
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dang hai » dang khai, hang hai, dung hai
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, mang may
van cac » van hac, van cau, van bac
va dang » van dang, va nang, va lang
cua tu » cua tuc, cua cu, cua te
cua su » qua su

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuat sach ky ((nang ma) or (nang cao)) hoi. hieu van cac nuoc va dang hai ((cua tu) OR (cua su))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach ky ((nang ma) OR (nang cao)) hoi. hieu van cac nuoc va dang hai ((cua tu) OR (cua su)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky ((nang ma) or (nang cao)) hoi. hieu van cac nuoc va dang hai ((cua tu) OR (cua su))".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky ((nang ma) or (nang cao)) hoi. hieu van cac nuoc va dang hai ((cua tu) OR (cua su))*.