Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
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, dan cac
van bac » van ban, van bao, van hac
va dang » van dang, va nang, va lang
hai cua » thai cua, dai cua, hoi cua
cua tu » cua tuc, cua su, cua cu

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) OR (van bac)) nuoc va dang hai cua tu~.
• 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) OR (van bac)) nuoc va dang hai cua tu.
• 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) OR (van bac)) nuoc va dang hai cua tu".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky ((nang ma) or (nang cao)) hoi. hieu ((van cac) OR (van bac)) nuoc va dang hai cua tu*.