Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
dang thai » dang thi, dang hai, dang khai
thai cua » than cua, tai cuc, tri cua
cac nuoc » cap nuoc, hoc nuoc, cua nuoc
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach ty
va dang » van dang, va nang, va lang
mang xa » lang xa, mang may, dang xay
cua te » cua tu

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 ((mang xa) or (nang ma)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) va dang thai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach ky ((mang xa) OR (nang ma)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) va dang thai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky ((mang xa) or (nang ma)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) va dang thai cua te".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky ((mang xa) or (nang ma)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) va dang thai cua te*.