Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
kem cua » em cua, keo cua, diem cua
duc van » duc va, duc tan, duc manh
hau duc » huu duc, ha duc, pham duc
van hau » van ha, van hai, van dau
cua tre » cua te, cuu tre, cua triet
ly nang » ky nang, ly hang, ly vang
y nang » ky nang, v nang, may 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) or (ly nang)) xa hoi. hieu van hau duc van hanh kem cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ((y nang) OR (ly nang)) xa hoi. hieu van hau duc van hanh kem cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ((y nang) or (ly nang)) xa hoi. hieu van hau duc van hanh kem cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ((y nang) or (ly nang)) xa hoi. hieu van hau duc van hanh kem cua tre*.