Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hanh day » hanh may, han day, hanh dao
te sach » toc sach
day cua » dai cua
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
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
v nang » va nang, vu nang, van 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 (hoc sach)) v nang ma hoi. ((hieu ve) OR (hieu va)) cam duc va hanh day cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (hoc sach)) v nang ma hoi. ((hieu ve) OR (hieu va)) cam duc va hanh day cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (hoc sach)) v nang ma hoi. ((hieu ve) OR (hieu va)) cam duc va hanh day cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (hoc sach)) v nang ma hoi. ((hieu ve) OR (hieu va)) cam duc va hanh day cua tre*.