Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
hanh di » hanh vi, hanh de, hang di
hoc duc » hoc duoc, hoc nuoc, hoc thuc
hac duc » ha duc, thach duc, pham duc
sach ty » sach y, sach tu, sach thu
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
di cua » dai cua, doi cua, de cua
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((nang ma) or (tang ma)) hoi. hieu qua ((hac duc) OR (hoc duc)) van hanh di cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang ma) OR (tang ma)) hoi. hieu qua ((hac duc) OR (hoc duc)) van hanh di 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 qua ((hac duc) OR (hoc duc)) van hanh di cua tu*".