Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
va thanh » gia thanh, ban thanh, le thanh
vu sach » vu bach, su sach, vu khach
ky lang » ky dang, ky tang, tay lang
va tinh » may tinh
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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

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