Perhaps you should try some spelling variations:
thieu bien » thieu nien, tieu bieu, hien bien
cua viet » ca viet, hoa viet, cua vat
van hanh » van thanh, ban hanh, van anh
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
sach ky » sac ky, sach y, sach ty
cac luc » cau luc, coc luc, cac cuoc
nang xa » lang xa, nang ma, mang xa
tu sach » thu sach, su sach, te sach
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((nang xa) or (nang x)) hoi. thieu bien ((cac luc) OR (cac nuoc)) van hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang x)) hoi. thieu bien ((cac luc) OR (cac nuoc)) van hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (nang x)) hoi. thieu bien ((cac luc) OR (cac nuoc)) van hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (nang x)) hoi. thieu bien ((cac luc) OR (cac nuoc)) van hanh vi cua viet*.