Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
tang ma » tang van
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
ve cac » va cac, vien cac
vi cua » vai cua, di cua

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 y ((tang ma) OR (mang may)) hoi. hieu ve cac duc van hanh vi cua vat~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((tang ma) OR (mang may)) hoi. hieu ve cac duc van hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((tang ma) OR (mang may)) hoi. hieu ve cac duc van hanh vi cua vat*.