Perhaps you should try some spelling variations:
hanh dai » hanh tai, hanh dao, vanh dai
dang xay » dang van, van xay
dich hoc » sinh hoc, hinh hoc, tinh hoc
cach hoc » cach thuc, cach thoi, cac hop
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
va hanh » van hanh, va thanh, va danh
te sac » te sach, te cac, te san
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: te sac ky ((nang xa) or (dang xay)) hoi. hieu va ((cach hoc) OR (dich hoc)) va hanh dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky ((nang xa) OR (dang xay)) hoi. hieu va ((cach hoc) OR (dich hoc)) va hanh dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky ((nang xa) or (dang xay)) hoi. hieu va ((cach hoc) OR (dich hoc)) va hanh dai cua te".
• Adding a wildcard symbol may retrieve word variants: te sac ky ((nang xa) or (dang xay)) hoi. hieu va ((cach hoc) OR (dich hoc)) va hanh dai cua te*.