Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tu sach » thu sach, su sach, te sach
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
sang ma » nang ma, sang tao, mang may
va cua » va chua, via cua, ca cua
cua te » cua tu

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) or (toc sach)) ky ((sang ma) or (tang ma)) hoi. hieu va cac duc va hanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky ((sang ma) OR (tang ma)) hoi. hieu va cac duc va hanh va cua te.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky ((sang ma) or (tang ma)) hoi. hieu va cac duc va hanh va cua te*.