Perhaps you should try some spelling variations:
thieu nien » thien nhien
hieu vien » hieu hien, hieu viec, hieu tieng
danh hai » dang hai, lanh hai, manh hai
tu sach » thu sach, te sach, tu cach
hai cua » thai cua, dai cua, hoi cua
va danh » va dinh, va dan, va hanh
cac lao » ca lao, cac loai, cac giao
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
su sach » so sach, vu sach
ma hoi » mai hoi, xa hoi, ma hoa
lao va » tao va, cao va, bao va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (su sach)) ky nang ma hoi. ((hieu vien) OR (thieu nien)) cac lao va danh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang ma hoi. ((hieu vien) OR (thieu nien)) cac lao va danh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky nang ma hoi. ((hieu vien) OR (thieu nien)) cac lao va danh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky nang ma hoi. ((hieu vien) OR (thieu nien)) cac lao va danh hai cua tre*.