Perhaps you should try some spelling variations:
hanh dai » hanh tai, hanh dao, vanh dai
toc sach » hoc sach, doc sach, thuoc sach
va hanh » van hanh, va thanh, va danh
cam duc » cam xuc, cao duc, pham duc
hieu va » lieu va, hieu qua
hieu ve » hieu van
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
y nang » ky nang, ly nang, v nang

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

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