Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
trung va » truong va, trang va, trung ha
hai cua » thai cua, dai cua, hoi cua
su sach » so sach, vu sach
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
cua tre » cua te, cuu tre, cua triet

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

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