Perhaps you should try some spelling variations:
duc tang » duc thang, duc tan, tuc tang
te sach » toc sach
hanh di » hanh de, hang di, danh di
cac duc » cac du, cao duc, cac dac
sach ly » sach y, sach lo, sach ty
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
ve cac » va cac, vien cac
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 ly ((nang ma) or (tang ma)) hoi. hieu ve cac duc tang ((hanh di) OR (hanh vi)) cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ly ((nang ma) OR (tang ma)) hoi. hieu ve cac duc tang ((hanh di) OR (hanh vi)) cua tu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ly ((nang ma) or (tang ma)) hoi. hieu ve cac duc tang ((hanh di) OR (hanh vi)) cua tu*".