Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
cua viet » ca viet, hoa viet, cua vat
ty nang » ky nang, ty xang, ty hang
cao hoi » cau hoi, co hoi, cao hoc
van cac » van cau, van bac, dan cac
van hac » van hoc, van ha, van hai
va hanh » van hanh, va thanh, va danh
dac va » duc va, day va, dat va
vi cua » vai cua, di cua

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) OR (doc sach)) ty nang cao hoi. hieu ((van cac) OR (van hac)) dac va hanh vi cua viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ty nang cao hoi. hieu ((van cac) or (van hac)) dac va hanh vi cua viet~".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ty nang cao hoi. hieu ((van cac) or (van hac)) dac va hanh vi cua viet*.