Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
hac duc » hoc duc, ha duc, thach duc
duc van » duc va, duc tan, duc manh
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 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 hanh di cua tu*.