Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
cac nuoc » hoc nuoc, dat nuoc, cua nuoc
dang hai » dang khai, hang hai, dung hai
cap nuoc » dat nuoc
hieu van » hieu va, thien van, lieu va
hai cua » thai cua, dai cua, hoi cua
va dang » van dang, va nang, va lang
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, mang may
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 nuoc) OR (cap 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 nuoc) OR (cap 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 nuoc) OR (cap 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 nuoc) OR (cap nuoc)) va dang hai cua tu*.