Perhaps you should try some spelling variations:
khac duan » nhac dan, khau luan, khai tuan
van hanh » van thanh, ban hanh, van anh
khac duc » khac phuc, khac cuoc, thach duc
te sach » toc sach
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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

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