Perhaps you should try some spelling variations:
thuat sac » thuat sach, thuat san, thuat tac
dang khai » dang khoi, dang hai, quang khai
cac nuoc » cap nuoc, hoc nuoc, cua nuoc
khai cua » thai cua, hai cua, khi cua
van dang » van dong, van dung, van nang
hieu van » hieu va, thien van, lieu va
nang xa » lang xa, nang ma, mang xa
sac ky » cac ky, sai ky
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 sac ky ((nang xa) or (nang x)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) van dang khai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sac ky ((nang xa) OR (nang x)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) van dang khai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sac ky ((nang xa) or (nang x)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) van dang khai cua te".
• Adding a wildcard symbol may retrieve word variants: thuat sac ky ((nang xa) or (nang x)) hoi. hieu van ((cac nuoc) OR (dat nuoc)) van dang khai cua te*.