Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
van hoi » van hoa, van hoe, van loi
van hoc » van hoa
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
va hanh » van hanh, va thanh, va danh
hanh de » hanh ve, hanh kem
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
de cua » le cua, te cua, dieu cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) or (doc sach)) y nang ((van hoi) OR (van hoc)). hieu va pham duc va hanh de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) y nang ((van hoi) OR (van hoc)). hieu va pham duc va hanh de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) y nang ((van hoi) OR (van hoc)). hieu va pham duc va hanh de cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) y nang ((van hoi) OR (van hoc)). hieu va pham duc va hanh de cua tre*.