Perhaps you should try some spelling variations:
hieu luan » hieu luat, hieu quan, tieu luan
van hanh » van thanh, ban hanh, van anh
phan duc » pham duc, phan dau, tran duc
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
su viet » so viet
vi su » va su, ve su, ki su

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 ty ((nang xa) or (lang xa)) hoi. hieu luan ((phan duc) OR (phan tu)) van hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (lang xa)) hoi. hieu luan ((phan duc) OR (phan tu)) van hanh vi su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang xa) or (lang xa)) hoi. hieu luan ((phan duc) OR (phan tu)) van hanh vi su viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (lang xa)) hoi. hieu luan ((phan duc) OR (phan tu)) van hanh vi su viet*.