Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
duc van » duc va, duc manh, duc phan
hanh di » hanh vi, hanh de, hang di
va hac » van hac, va khac, va cac
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.

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