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