Perhaps you should try some spelling variations:
thuat sac » thuat sach, thuat san, thuat tac
hieu van » hieu va, thien van, lieu va
cau nuoc » cap nuoc, cac nuoc, dau nuoc
van dang » van dung, van nang, van dan
nang xa » nang x, lang xa, nang ma
sang ma » tang ma, nang ma, sang tao
van cau » van dau, van hau, van chat
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 (sang ma)) hoi. hieu van cau nuoc ((van dang) OR (van dong)) tri cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sac ky ((nang xa) OR (sang ma)) hoi. hieu van cau nuoc ((van dang) OR (van dong)) tri cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sac ky ((nang xa) or (sang ma)) hoi. hieu van cau nuoc ((van dang) OR (van dong)) tri cua te".
• Adding a wildcard symbol may retrieve word variants: thuat sac ky ((nang xa) or (sang ma)) hoi. hieu van cau nuoc ((van dang) OR (van dong)) tri cua te*.